Levent Kabasakal - Academia.edu (original) (raw)
Papers by Levent Kabasakal
Thyroid and Parathyroid Diseases, 2018
The widespread use of imaging modalities such as ultrasonography (USG), magnetic resonance imagin... more The widespread use of imaging modalities such as ultrasonography (USG), magnetic resonance imaging (MRI), and computer tomography (CT) has significantly increased thyroid nodule detection. Thyroid nodules are generally benign, but identification of malignant nodules is an important clinical problem. Nodules with hyperfunction on thyroid scintigraphy, also known as autonomously functioning thyroid nodules (AFTNs), are often considered as benign.
Thyroid and Parathyroid Diseases, 2018
With the common use of imaging modalities such as ultrasonography (USG), the incidence of thyroid... more With the common use of imaging modalities such as ultrasonography (USG), the incidence of thyroid cancer has increased in recent years. Most of the thyroid cancers are differentiated thyroid cancers (DTC). In the case of DTC, the ability of cancer cells to concentrate iodine makes radioactive iodine (RAI) therapy possible, which is an effective treatment for DTCs. Surgical operation and RAI treatment give a chance to be cured for many thyroid cancer patients. Nonetheless, resistance to RAI treatment develops in a group of patients, and the prognosis worsens. In RAI-refractory (RAI-R) DTC patients, chemotherapeutic drugs such as doxorubicin and cisplatin have been tried, but no successful results have been obtained. In contrast, multiple kinase inhibitors (MKIs) have provided for RAI-R patients a new treatment option. Sorafenib and lenvatinib have been approved by the FDA for RAI-R DTC patients, and phase studies of other MKIs are ongoing.
Nuclear Medicine Seminars, 2021
Somatostatin analogues labeled with peptide receptor radionuclide therapy (PRRT) have a long hist... more Somatostatin analogues labeled with peptide receptor radionuclide therapy (PRRT) have a long history in the treatment of neuroendocrine tumor (NET). Lu-177 DOTA TATE, whose efficacy has been proven by phase studies, is a treatment method that is easily tolerated by patients and has a low side-effect profile compared to alternative chemotherapeutics. After the success of Lu-177 DOTA TATE, alpha therapy (AT) was recommended to patients with clinically and histologically more aggressive tumors in order to increase the effectiveness of treatment via the same receptor. Pioneering publications on Ac-225 DOTA TATE therapy are promising for the future of therapy.
Thyroid and Parathyroid Diseases, 2018
Nuclear Medicine Seminars, 2020
Peptit reseptör radyonüklit tedavisi (PRRT) 20 yıldır ileri evre veya metastatik nöroendokrin tüm... more Peptit reseptör radyonüklit tedavisi (PRRT) 20 yıldır ileri evre veya metastatik nöroendokrin tümörlerin tedavisinde yaygın olarak kullanılmaktadır. Retrospektif ve prospektif birçok çalışma ile yüksek yanıt oranlarının yanı sıra sağkalıma ve yaşam kalitesine katkısı gösterilmiştir. PRRT hasta tarafından kolay tolere edilen, kabul edilebilir hematolojik toksisitesi olan bir tedavi yöntemidir. Nefrotoksisite ise daha az kullanılan Y-90 işaretli peptitlerde doz limitleyici olmakla birlikte Lu-177 işaretli peptitlerde ise oldukça sınırlı düzeyde kalmaktadır. PRRT genellikle standart protokollerle hastaların klinik durumu, risk faktörleri ve dozimetrik çalışmalarına göre kısmi olarak değiştirilen standart protokoller çerçevesinde uygulanır. Bu uygulama kılavuzunun amacı, nükleer tıp uzmanlarına PRRT'nin temel yaklaşımları, endikasyonları, kontrendikasyonları, tedavi yanıtı değerlendirmesi ve tedavi sonrası hasta takibinde yardımcı olmaktır. AnahtarKelimeler: 177Lu-DOTATATE, nöroendokrin tümörler, peptit reseptör radyonüklit tedavi Peptide receptor radionuclide therapy (PRRT) have been successfully used for the past 20 years to target metastatic or inoperable neuroendocrine tumors expressing the somatostatin receptors. Both prospective and retrospective studies indicate that patients receiving PRRT show significantly high objective responses, leading to longer survival and improved quality of life. PRRT is generally well tolerated, with acceptable hematological toxicity profiles. Nephrotoxicity is dose-limiting with Y-90 labelled peptides and not with Lu-177. The majority of centers use standard protocols based on fixed activities, at most modulating the activity or the number of administrations based on the patient clinical scenario and risk factors. This guidance covers the rationale, indications and contraindications for PRRNT, assessment of treatment response and patient follow-up. This practical guidance is aimed at guiding nuclear medicine specialists in delivering the treatment in a safe and effective manner.
Urology journal, 2020
PURPOSE To determine whether a 68Ga-PSMA PET/CT scan evaluation before radical prostatectomy (RP)... more PURPOSE To determine whether a 68Ga-PSMA PET/CT scan evaluation before radical prostatectomy (RP) is an effective imaging modality for clinical local and lymph node (LN) staging compared with the pathological results. MATERIALS AND METHODS We performed a preoperative 68Ga-PSMA PET/CT scan in 51 patients with prostate cancer (PCa), who were scheduled for an RP operation between January 2014 and June 2016 in our clinic. The correlation between the RP pathology and the results of the 68Ga-PSMA PET/CT scan was investigated. RESULTS When the 68Ga-PSMA PET/CT scan results were evaluated according to the risk groups, intraprostatic activity was found in 5 of 12 patients (41.7%) in the low-risk group, 15 of 19 patients in the intermediate risk group (78.9%), and 90% patients in the high-risk group. The 68Ga-PSMA PET/CT scan sensitivity, specificity, positive and negative predictive values and accuracy were calculated as 58.2%, 75.3%, 84.4%, 44%, and 63%, respectively for intraprostatic tumo...
Purpose To assess frequency, clinical indications, and cumulative effective dose (CED) of patient... more Purpose To assess frequency, clinical indications, and cumulative effective dose (CED) of patients undergoing multiple 18F-FDG PET/CT imaging. Methods Retrospective analysis of 18F-FDG PET/CT scans performed at a University hospital for 11 years was done. Effective dose was computed from activity administered and dose-length-product. Results A total of 55,424 18F-FDG PET/CT scans were performed in 32,658 patients. The average injected activity was 421 MBq and median 417 MBq. 24.2% of the patients were scanned 2-5 times in a year, 16.7% of them being unique patients (not counted as separate patient in different years). The maximum PET/CT scans in a year was five. 23571 (72.2 %) patients underwent a single 18F-FDG PET/CT scan, while 9087 (27.8%) unique patients underwent 2 - 23 scans during 11 years. 82% of the scanned patients had malignant disease, 2.4% among the patients with ≥ 2 18F-FDG PET/CT scans in a year were with non-malignant indications. 1.4% of patients received CED ≥100 ...
European Journal of Nuclear Medicine and Molecular Imaging, 2021
Prostate-specific membrane antigen (PSMA)-based radioligand therapy (RLT) showed in a multicentre... more Prostate-specific membrane antigen (PSMA)-based radioligand therapy (RLT) showed in a multicentre WARMTH (World Association of Radiopharmaceutical and Molecular Therapy) study that the presence of bone metastases is a negative prognosticator for the survival. The current multicentre retrospective analysis aims to evaluate the response rate to RLT, the overall survival (OS) of patients and the safety of the treatment according to the extent of bone involvement. The study included patients with progressive metastatic castration-resistant prostate cancer (mCRPC), who underwent RLT with [177Lu]Lu-PSMA-617 and a follow-up of at least 6 months. Tumour burden in the bone was classified prior to RLT as follows: less than 6 lesions, 6–20 lesions, more than 20 lesions and diffuse involvement. The response rate was evaluated using changes of the prostate-specific antigen (PSA) after the first treatment cycle. Overall survival was calculated from the date of the first treatment. Haematological adverse events were classified according to Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. A total of 319 males were included in the analysis. The extent of bone metastases and PSA response did not correlate significantly. Any PSA decline was observed in 73% patients; 44% showed a decline of ≥50%. The median OS of patient in the different subgroups was 18 months (less than 6 lesions), 13 months (6–20 lesions), 11 months (more than 20 lesions) and 8 months (diffuse involvement), respectively (p < 0.0001). Patients with prior Ra-223-therapy showed longer OS in all subgroups, especially in the subgroups with 6–20 lesions (OS: 16 vs. 12 months; p = 0.038) as well as diffuse involvement (OS: 11 vs. 7 months; p = 0.034). Significant negative prognosticators of OS were the existence of liver metastases in all subgroups and prior chemotherapy in patients with <6 bone lesions. Anaemia and thrombocytopenia correlated positively with the extent of bone metastases: p < 0.0001 and 0.005, respectively. No patient showed a high grade leukopenia. The extent of bone involvement correlated negatively with the OS after RLT; however, it showed no relevant correlation with the PSA response rate. Prior therapy with Ra-223 may have a positive impact on OS. Haematotoxicity was higher in patients with more than 20 bone lesions; nevertheless, the majority of these patients did not show a relevant haematotoxicity.
![Research paper thumbnail of Prior therapies as prognostic factors of overall survival in metastatic castration-resistant prostate cancer patients treated with [177Lu]Lu-PSMA-617. A WARMTH multicenter study (the 617 trial)](https://attachments.academia-assets.com/99821397/thumbnails/1.jpg)
](European Journal of Nuclear Medicine and Molecular Imaging, 2020
Introduction The impact of prior therapies, especially chemotherapy, on overall survival (OS) in ... more Introduction The impact of prior therapies, especially chemotherapy, on overall survival (OS) in patients with castration-resistant prostate cancer (CRPC) receiving [177Lu]Lu-PSMA-617 therapy has been the subject of controversy. Therefore, WARMTH decided to plan a multicenter retrospective analysis (the “617 trial”) to evaluate response rate and OS as well as the impact of prior therapies on OS in more than 300 patients treated with 177Lu-PSMA-617. Materials and methods The data of 631 metastatic CRPC (mCRPC) patients from 11 different clinics were evaluated. According to the inclusion and exclusion criteria, all patients had to have received at least abiraterone or enzalutamide prior to [177Lu]Lu-PSMA-617 therapy. The patients were divided into three groups: patients who had received prior chemotherapy, patients who avoided chemotherapy, and patients for whom a chemotherapy was contraindicated. Results The analysis included the data of 416 patients, with a median age of 71.9 years....
European Journal of Nuclear Medicine and Molecular Imaging, 2020
Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in publishe... more Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Clinical Imaging, 2019
To assess the ability of diffusion-weighted imaging (DWI) in predicting the overall survival in p... more To assess the ability of diffusion-weighted imaging (DWI) in predicting the overall survival in patients who underwent Yttrium 90 radioembolization (90 Y-RE) for colorectal liver metastases (CLM) with other well-established clinical and imaging parameters by comparing the pre-and post-treatment apparent diffusion coefficient (ADC) values of the lesions. Methods: A total of 81 metastatic lesions of 27 consecutive patients who underwent DWI before and after the 90 Y-RE session were enrolled in the study. ADC values were calculated from the entire (ADC e) and peripheral (ADC p) tumor on pre-and post-treatment DWI, and any relative increase in ADC > 0% accepted as a functional imaging response. The impact of functional imaging response in addition to other well-known parameters including Response Evaluation Criteria in Solid Tumors (RECIST), hepatic tumor burden, Eastern Cooperative Oncology Group performance status (ECOG-PS) and the presence of extrahepatic metastases in predicting overall survival (OS) was assessed using Kaplan-Meier curves and Cox-regression analyses. Results: The median OS of the patients was 10 months (range, 6-20 months) while the median OS of the responders being significantly longer than the non-responders for ADC e and ADC p (median 11 vs 7 months, P = 0.003; median 12 vs. 7 months, P < 0.0001, respectively). The RECIST score was also significantly affected the OS (progressive or stable disease median 8 months vs. partial response 15 indent months, P = 0.019). The other parameters including hepatic tumor burden, gender, ECOG score, the involvement of the liver lobes, and the presence of extrahepatic metastases were not associated with the OS. In multivariate analysis, only ADC p remained as an independent predictor of OS (P = 0.003, HR = 19.878). Conclusion: Any increase in relative ADC p or ADC e values after Y90-RE treatment was associated with longer OS in CLM patients, and DWI seems to be valuable imaging biomarker in predicting OS in CLM patients during the early post-interventional period after 90 Y-RE.
Nuclear Medicine Seminars, 2018
Metastatik ve kastrasyona dirençli prostat kanseri (mKDPK) tedavisinde son yıllarda ciddi gelişme... more Metastatik ve kastrasyona dirençli prostat kanseri (mKDPK) tedavisinde son yıllarda ciddi gelişmeler olmaktadır. Yeni geliştirilen ilaçların da etkisiyle (örneğin; Enzalutamide, abiraterone) mKDPK'de sağkalım süreleri her geçen yıl artış göstermektedir. Ancak yeni nesil tedavi seçeneklerine 1-2 yıl içerisinde direnç gelişmekte ve bu aşamadan sonra sağkalım süreleri belirgin olarak kısalmaktadır (1). Bu grup hastalarda ise Ra-223 ve Lu-177 prostat spesifik membran antijeni (PSMA) tedavilerinin kullanımı her geçen gün artmaktadır (2,3). PSMA diğer adı glutamat karboksipeptidaz II olan ve hücre içerisinde enzim fonksiyonları bulunan bir transmembran glikoproteindir ve yaklaşık 30 yıl kadar önce bulunmuştur. Folat'ın hücre içine alınmasında rolü olduğu gibi hücre migrasyonu, hücre sağkalım ve proliferasyonunda da görev alır. Sağlıklı prostat epitel hücrelerinde düşük düzeyde ekspresyonu bulunmakla birlikte prostat kanserinde 1000 kata varan oranlarda daha fazla bulunabilmektedir (4). Bu durum PSMA molekülünü prostat kanseri tanı ve tedavisinde radyofarmasötikler için hedef haline Metastatik ve kastrasyona dirençli prostat kanseri tedavisinde Lu-177 prostat spesifik membran antijeni (PSMA) tedavisi son yıllarda başarı ile uygulanmaya başlamış ve hızla yaygınlaşmıştır. Lu-177 PSMA tedavisi belirgin ağrı palyasyonu ve hasta performans skorlarında artış sağlarken, %44-60 oranlarında serum prostat spesifik antijen (PSA) seviyelerinde >%50 düşüş bildirilmiştir. Retrospektif serilerin meta-analizine göre 3. basamak sistemik tedavi seçeneklerinden daha uzun sağkalım ve daha yüksek oranda PSA yanıtları elde edilmektedir. Bu sonuçlara ise kontrol edilebilir bir yan etki profili ile ulaşılmaktadır. Bu derlemede Lu-177 PSMA tedavisinin hangi hasta gruplarında, ne zaman, hangi dozlarda uygulanacağından bahsedilecek olup tedavinin pratik uygulama yönleri, tedavi yanıtları ve yan etkileri tartışılacaktır.
Nuclear Medicine Communications, 2018
Purpose The intensity of prostate-specific membrane antigen (PSMA) expression increases as the tu... more Purpose The intensity of prostate-specific membrane antigen (PSMA) expression increases as the tumor grade increases and the uptake of Ga-68-PSMA is higher in highgrade tumors. The aim of the present study was to evaluate the correlation of preoperative tracer uptake of primary tumor to Gleason Score in patients who underwent prostatectomy. Patients and methods We retrospectively evaluated 141 patients who had Ga-68-PSMA positron emission tomography/computed tomography (PET/CT) imaging and who underwent prostatectomy. All patients had a diagnosis of prostate cancer on the basis of 10-24 cores transrectal ultrasound-guided biopsy (TRUS-Bx). Histological assessment was performed according to the New Contemporary Prostate Cancer Grading System. All patients had a prostate-specific antigen (PSA) level measurement within maximum of 28 days before Ga-68-PSMA PET/CT. Region of interests were drawn manually around the prostate gland, avoiding the bladder activity, to calculate the maximum standardized uptake values (SUVmax) values. Results The median PSA values for all patients were 10.0 ng/ml. PSA values for low-risk patients were significantly lower than those of high-risk patients (P < 0.001). There were 41.1% upgrades and 7.8% downgrades following prostatectomy in terms of Grade Groups. According to the final pathology reports, 21% (n = 16) of patients moved from a low-risk level (grade groups 1 + 2) to a high-risk level (grade groups 3 + 4 + 5). The median SUVmax value was 8.8, ranging from 2.1 to 62.4. There was a strong correlation between SUVmax values and grade groups (Pearson ρ = 0.66) (P < 0.001). The mean SUVmax values of high-risk patients were significantly higher than those of low-risk patients (18.9 ± 12.1 vs. 7.16 ± 6.2, respectively) (P < 0.001). Receiver operation characteristic curve analysis of SUVmax at the cutoff value of 9.1 showed a high sensitivity (78%) and specificity (81%) for detection of high risk disease. Conclusion SUVmax values correlate significantly with the grade groups of the primary tumor. The intraprostatic accumulation sites may predict clinically significant cancer and potentially serve as a target for biopsy sampling in conjunction with mpMRI in selected patients. Nucl Med Commun 40:86
Radiation and environmental biophysics, Jan 8, 2018
The aim of the present study was to review the available models developed for calculating red bon... more The aim of the present study was to review the available models developed for calculating red bone marrow dose in radioiodine therapy using clinical data. The study includes 18 patients (12 females and six males) with metastatic differentiated thyroid cancer. Radioiodine tracer of 73 ± 16 MBq I was orally administered, followed by blood sampling (2 ml) and whole-body scans (WBSs) done at several time points (2, 6, 24, 48, 72, and ≥ 96 h). Red bone marrow dose was estimated using the OLINDA/EXM 1.0, IDAC-Dose 2.1, and EANM models, the models developed by Shen and co-workers, Keizer and co-workers and Siegel and co-workers, and Traino and co-workers, as well as the single measurement model (SMM). The results were then compared to the standard reference model Revised Sgouros Model (RSM) reported by Wessels and co-workers. The mean dose deviations of the Traino, Siegel, Shen, Keizer, OLINDA/EXM, EANM, SMM, and IDAC-Dose 2.1 models from the RSM were - 17%, - 24%, 6%, - 29%, - 15%, 40%, 4...
Nuclear medicine communications, 2018
The development of reliable dosimetry models promotes the individualized therapy concept toward m... more The development of reliable dosimetry models promotes the individualized therapy concept toward more success and less complications. This paper evaluates the traditional maximum empirical activity (250 mCi) and the benefit of joining two dosimetry approaches to optimize the therapeutic activity and radioiodine efficacy in metastatic differentiated thyroid cancer. Nineteen (12 females and seven males) patients with metastatic differentiated thyroid cancer were included in the present study. The mean age of the patients was 46±16 years. The mean height and weight were 1.67±0.11 m and 76±18 kg, respectively. Radioiodine treatment was given by recombinant human thyrotropin stimulation in seven patients, and thyroxine withdrawal was successful for the rest 12 patients. The mean thyroid-stimulating hormone value was 68±34 μIU/ml, and the mean thyroglobulin value was 408±356 ng/ml before therapy. After radiotracer administration, lesion-absorbed dose was calculated in addition to red marro...
Malecular Imaging and Radionuclide Therapy, 2017
Objective: The aim of the study was to estimate the radiation-absorbed doses and to study the in ... more Objective: The aim of the study was to estimate the radiation-absorbed doses and to study the in vivo and in vitro stability as well as pharmacokinetic characteristics of lutetium-177 (Lu-177) prostate-specific membrane antigen (PSMA)-617. Methods: For this purpose, 7 patients who underwent Lu-177-PSMA therapy were included into the study. The injected Lu-177-PSMA-617 activity ranged from 3.6 to 7.4 GBq with a mean of 5.2±1.8 GBq. The stability of radiotracer in saline was calculated up to 48 h. The stability was also calculated in blood and urine samples. Post-therapeutic dosimetry was performed based on whole body and single photon emission computed tomography/computed tomography (SPECT/CT) scans on dualheaded SPECT/CT system. Results: The radiochemical yield of Lu-177-PSMA-617 was >99%. It remained stable in saline up to 48 h. Analyses of the blood and urine samples showed a single radioactivity peak even at 24 hours after injection. Half-life of the distribution and elimination phases were calculated to be 0.16±0.09 and 10.8±2.5 hours, respectively. The mean excretion rate was 56.5±8.8% ranging from 41.5% to 65.4% at 24 h. Highest radiation estimated doses were calculated for parotid glands and kidneys (1.90±1.19 and 0.82±0.25 Gy/GBq respectively). Radiation dose given to the bone marrow was significantly lower than those of kidney and parotid glands (p<0.05) (0.030±0.008 Gy/GBq). Conclusion: Lu-177-PSMA-617 is a highly stable compound both in vitro and in vivo. Lu-177-PSMA-617 therapy seems to be a safe method for the treatment of castration-resistant prostate cancer patients. The fractionation regime that enables the longest duration of tumor control and/or survival will have to be developed in further studies.
Nuclear Medicine Communications, 2017
Objective Prediction and early diagnosis of orbitopathy is needed in patients with Graves' diseas... more Objective Prediction and early diagnosis of orbitopathy is needed in patients with Graves' disease, especially when radioiodine therapy is planned. Positron emission tomography/computerized tomography (PET/CT) using flourine-18-fluorodeoxyglucose (FDG) is an effective imaging modality in detection of inflammation, however, its ability to detect orbital inflammation has not been well studied. The aim of our study is to determine the ability of FDG PET/CT to detect orbital inflammation related with Graves' disease, identify active orbitopathy, predict the radioiodine-triggered orbitopathy, and find out the effects of radioiodine on orbital inflammation. Materials and methods Total 31 Graves' disease patients and 17 controls were included. All Graves' disease patients underwent cranial FDG PET/CT imaging prior therapy. Radioiodine therapy and post-treatment PET/CT study was applied to 21 patients. PET/CT images of all examinees were evaluated, measuring extraocular muscle maximum standard uptake value (SUV max) and muscle thickness. Results FDG uptake was increased in the majority of extraocular muscles in Graves' disease patients in comparison to controls and this increase was found to be irrelevant from muscle thickness. Extraocular muscle SUV max values did not increase in Graves' orbitopathy patients who received radioiodine under corticosteroid prophylaxis. SUV max level of all orbital rectus muscles were increased after radioiodine therapy in nonsmokers, whereas no increase was detected in smokers. Conclusion FDG PET/CT may be helpful in detection of extraocular muscle inflammation and it may show ongoing orbitopathy in early stages of inflammation before anatomical changes occur. Nucl Med Commun
European journal of nuclear medicine and molecular imaging, Jan 18, 2017
To assess the diagnostic accuracy of (68)Ga-PSMA PET in predicting lymph node (LN) metastases in ... more To assess the diagnostic accuracy of (68)Ga-PSMA PET in predicting lymph node (LN) metastases in primary N staging in high-risk and very high-risk nonmetastatic prostate cancer in comparison with morphological imaging. This was a multicentre trial of the Society of Urologic Oncology in Turkey in conjunction with the Nuclear Medicine Department of Cerrahpasa School of Medicine, Istanbul University. Patients were accrued from eight centres. Patients with high-risk and very high-risk disease scheduled to undergo surgical treatment with extended LN dissection between July 2014 and October 2015 were included. Either MRI or CT was used for morphological imaging. PSMA PET/CT was performed and evaluated at a single centre. Sensitivity, specificity and accuracy were calculated for the detection of lymphatic metastases by PSMA PET/CT and morphological imaging. Kappa values were calculated to evaluate the correlation between the numbers of LN metastases detected by PSMA PET/CT and by histopath...
Nuclear Medicine Communications, 2017
Introduction Prostate-specific membrane antigen (PSMA) is increasingly being recognized as a nove... more Introduction Prostate-specific membrane antigen (PSMA) is increasingly being recognized as a novel target for the PET imaging of prostate cancer (PCa) and 68 Ga-DKFZ-11 (68 Ga-PSMA) has been suggested as a novel tracer for detection of PCa relapses and metastases. The aim of this study was to evaluate the diagnostic value of PSMA PET/CT in the diagnosis of recurrent PCa with low prostate-specific antigen (PSA) levels. Patients and methods We carried out a retrospective analysis of patients who underwent PSMA PET/CT from November 2013 to December 2014 in our department. Among these patients, 50 out of 178 who had increasing PSA levels (< 5 ng/ml) and did not have known metastasis were included in this study. Results Patients had an average PSA of 1.41 ng/ml. A total of 29 patients (58%) showed at least one positive lesion. PET positivity rates of 31% (n = 4), 54% (n = 13), and 88% (n = 14) were observed in patients with a PSA level of less than 0.2, 0.2-2, and 2-5 ng/ml, respectively. A positive correlation was observed between positivity rate and Gleason scores and blood PSA levels. Verification was performed in 46 patients, with biopsy (n = 3) and follow-up, and conventional imaging studies at the time of the PET/CT or during follow-up with a mean period of 10.6 ± 3.3 months and ranged from 3.8 to 16.4 months. According to patientbased analysis of 46 cases, 57% of patients had true positive, 24% of patients had true negative, 2% of patients had false positive, an 18% of patients had false-negative findings. A sensitivity of 76.47% (95% confidence interval: 58.83-89.25%) and a specificity of 91.67% (95% confidence interval: 61.52-99.79%) were found. Conclusion PET/CT with 68 Ga-PSMA is a valuable tool for assessing recurrence of PCa with a high sensitivity in patients who have PSA levels between 0.2 and 5 ng/ml. In addition, this study suggests that PSMA PET/CT can be used in patients with very low (< 0.2 ng/ml) but increasing PSA levels, which, in many cases, may influence further clinical management.
Thyroid and Parathyroid Diseases, 2018
The widespread use of imaging modalities such as ultrasonography (USG), magnetic resonance imagin... more The widespread use of imaging modalities such as ultrasonography (USG), magnetic resonance imaging (MRI), and computer tomography (CT) has significantly increased thyroid nodule detection. Thyroid nodules are generally benign, but identification of malignant nodules is an important clinical problem. Nodules with hyperfunction on thyroid scintigraphy, also known as autonomously functioning thyroid nodules (AFTNs), are often considered as benign.
Thyroid and Parathyroid Diseases, 2018
With the common use of imaging modalities such as ultrasonography (USG), the incidence of thyroid... more With the common use of imaging modalities such as ultrasonography (USG), the incidence of thyroid cancer has increased in recent years. Most of the thyroid cancers are differentiated thyroid cancers (DTC). In the case of DTC, the ability of cancer cells to concentrate iodine makes radioactive iodine (RAI) therapy possible, which is an effective treatment for DTCs. Surgical operation and RAI treatment give a chance to be cured for many thyroid cancer patients. Nonetheless, resistance to RAI treatment develops in a group of patients, and the prognosis worsens. In RAI-refractory (RAI-R) DTC patients, chemotherapeutic drugs such as doxorubicin and cisplatin have been tried, but no successful results have been obtained. In contrast, multiple kinase inhibitors (MKIs) have provided for RAI-R patients a new treatment option. Sorafenib and lenvatinib have been approved by the FDA for RAI-R DTC patients, and phase studies of other MKIs are ongoing.
Nuclear Medicine Seminars, 2021
Somatostatin analogues labeled with peptide receptor radionuclide therapy (PRRT) have a long hist... more Somatostatin analogues labeled with peptide receptor radionuclide therapy (PRRT) have a long history in the treatment of neuroendocrine tumor (NET). Lu-177 DOTA TATE, whose efficacy has been proven by phase studies, is a treatment method that is easily tolerated by patients and has a low side-effect profile compared to alternative chemotherapeutics. After the success of Lu-177 DOTA TATE, alpha therapy (AT) was recommended to patients with clinically and histologically more aggressive tumors in order to increase the effectiveness of treatment via the same receptor. Pioneering publications on Ac-225 DOTA TATE therapy are promising for the future of therapy.
Thyroid and Parathyroid Diseases, 2018
Nuclear Medicine Seminars, 2020
Peptit reseptör radyonüklit tedavisi (PRRT) 20 yıldır ileri evre veya metastatik nöroendokrin tüm... more Peptit reseptör radyonüklit tedavisi (PRRT) 20 yıldır ileri evre veya metastatik nöroendokrin tümörlerin tedavisinde yaygın olarak kullanılmaktadır. Retrospektif ve prospektif birçok çalışma ile yüksek yanıt oranlarının yanı sıra sağkalıma ve yaşam kalitesine katkısı gösterilmiştir. PRRT hasta tarafından kolay tolere edilen, kabul edilebilir hematolojik toksisitesi olan bir tedavi yöntemidir. Nefrotoksisite ise daha az kullanılan Y-90 işaretli peptitlerde doz limitleyici olmakla birlikte Lu-177 işaretli peptitlerde ise oldukça sınırlı düzeyde kalmaktadır. PRRT genellikle standart protokollerle hastaların klinik durumu, risk faktörleri ve dozimetrik çalışmalarına göre kısmi olarak değiştirilen standart protokoller çerçevesinde uygulanır. Bu uygulama kılavuzunun amacı, nükleer tıp uzmanlarına PRRT'nin temel yaklaşımları, endikasyonları, kontrendikasyonları, tedavi yanıtı değerlendirmesi ve tedavi sonrası hasta takibinde yardımcı olmaktır. AnahtarKelimeler: 177Lu-DOTATATE, nöroendokrin tümörler, peptit reseptör radyonüklit tedavi Peptide receptor radionuclide therapy (PRRT) have been successfully used for the past 20 years to target metastatic or inoperable neuroendocrine tumors expressing the somatostatin receptors. Both prospective and retrospective studies indicate that patients receiving PRRT show significantly high objective responses, leading to longer survival and improved quality of life. PRRT is generally well tolerated, with acceptable hematological toxicity profiles. Nephrotoxicity is dose-limiting with Y-90 labelled peptides and not with Lu-177. The majority of centers use standard protocols based on fixed activities, at most modulating the activity or the number of administrations based on the patient clinical scenario and risk factors. This guidance covers the rationale, indications and contraindications for PRRNT, assessment of treatment response and patient follow-up. This practical guidance is aimed at guiding nuclear medicine specialists in delivering the treatment in a safe and effective manner.
Urology journal, 2020
PURPOSE To determine whether a 68Ga-PSMA PET/CT scan evaluation before radical prostatectomy (RP)... more PURPOSE To determine whether a 68Ga-PSMA PET/CT scan evaluation before radical prostatectomy (RP) is an effective imaging modality for clinical local and lymph node (LN) staging compared with the pathological results. MATERIALS AND METHODS We performed a preoperative 68Ga-PSMA PET/CT scan in 51 patients with prostate cancer (PCa), who were scheduled for an RP operation between January 2014 and June 2016 in our clinic. The correlation between the RP pathology and the results of the 68Ga-PSMA PET/CT scan was investigated. RESULTS When the 68Ga-PSMA PET/CT scan results were evaluated according to the risk groups, intraprostatic activity was found in 5 of 12 patients (41.7%) in the low-risk group, 15 of 19 patients in the intermediate risk group (78.9%), and 90% patients in the high-risk group. The 68Ga-PSMA PET/CT scan sensitivity, specificity, positive and negative predictive values and accuracy were calculated as 58.2%, 75.3%, 84.4%, 44%, and 63%, respectively for intraprostatic tumo...
Purpose To assess frequency, clinical indications, and cumulative effective dose (CED) of patient... more Purpose To assess frequency, clinical indications, and cumulative effective dose (CED) of patients undergoing multiple 18F-FDG PET/CT imaging. Methods Retrospective analysis of 18F-FDG PET/CT scans performed at a University hospital for 11 years was done. Effective dose was computed from activity administered and dose-length-product. Results A total of 55,424 18F-FDG PET/CT scans were performed in 32,658 patients. The average injected activity was 421 MBq and median 417 MBq. 24.2% of the patients were scanned 2-5 times in a year, 16.7% of them being unique patients (not counted as separate patient in different years). The maximum PET/CT scans in a year was five. 23571 (72.2 %) patients underwent a single 18F-FDG PET/CT scan, while 9087 (27.8%) unique patients underwent 2 - 23 scans during 11 years. 82% of the scanned patients had malignant disease, 2.4% among the patients with ≥ 2 18F-FDG PET/CT scans in a year were with non-malignant indications. 1.4% of patients received CED ≥100 ...
European Journal of Nuclear Medicine and Molecular Imaging, 2021
Prostate-specific membrane antigen (PSMA)-based radioligand therapy (RLT) showed in a multicentre... more Prostate-specific membrane antigen (PSMA)-based radioligand therapy (RLT) showed in a multicentre WARMTH (World Association of Radiopharmaceutical and Molecular Therapy) study that the presence of bone metastases is a negative prognosticator for the survival. The current multicentre retrospective analysis aims to evaluate the response rate to RLT, the overall survival (OS) of patients and the safety of the treatment according to the extent of bone involvement. The study included patients with progressive metastatic castration-resistant prostate cancer (mCRPC), who underwent RLT with [177Lu]Lu-PSMA-617 and a follow-up of at least 6 months. Tumour burden in the bone was classified prior to RLT as follows: less than 6 lesions, 6–20 lesions, more than 20 lesions and diffuse involvement. The response rate was evaluated using changes of the prostate-specific antigen (PSA) after the first treatment cycle. Overall survival was calculated from the date of the first treatment. Haematological adverse events were classified according to Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. A total of 319 males were included in the analysis. The extent of bone metastases and PSA response did not correlate significantly. Any PSA decline was observed in 73% patients; 44% showed a decline of ≥50%. The median OS of patient in the different subgroups was 18 months (less than 6 lesions), 13 months (6–20 lesions), 11 months (more than 20 lesions) and 8 months (diffuse involvement), respectively (p < 0.0001). Patients with prior Ra-223-therapy showed longer OS in all subgroups, especially in the subgroups with 6–20 lesions (OS: 16 vs. 12 months; p = 0.038) as well as diffuse involvement (OS: 11 vs. 7 months; p = 0.034). Significant negative prognosticators of OS were the existence of liver metastases in all subgroups and prior chemotherapy in patients with <6 bone lesions. Anaemia and thrombocytopenia correlated positively with the extent of bone metastases: p < 0.0001 and 0.005, respectively. No patient showed a high grade leukopenia. The extent of bone involvement correlated negatively with the OS after RLT; however, it showed no relevant correlation with the PSA response rate. Prior therapy with Ra-223 may have a positive impact on OS. Haematotoxicity was higher in patients with more than 20 bone lesions; nevertheless, the majority of these patients did not show a relevant haematotoxicity.
European Journal of Nuclear Medicine and Molecular Imaging, 2020
Introduction The impact of prior therapies, especially chemotherapy, on overall survival (OS) in ... more Introduction The impact of prior therapies, especially chemotherapy, on overall survival (OS) in patients with castration-resistant prostate cancer (CRPC) receiving [177Lu]Lu-PSMA-617 therapy has been the subject of controversy. Therefore, WARMTH decided to plan a multicenter retrospective analysis (the “617 trial”) to evaluate response rate and OS as well as the impact of prior therapies on OS in more than 300 patients treated with 177Lu-PSMA-617. Materials and methods The data of 631 metastatic CRPC (mCRPC) patients from 11 different clinics were evaluated. According to the inclusion and exclusion criteria, all patients had to have received at least abiraterone or enzalutamide prior to [177Lu]Lu-PSMA-617 therapy. The patients were divided into three groups: patients who had received prior chemotherapy, patients who avoided chemotherapy, and patients for whom a chemotherapy was contraindicated. Results The analysis included the data of 416 patients, with a median age of 71.9 years....
European Journal of Nuclear Medicine and Molecular Imaging, 2020
Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in publishe... more Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Clinical Imaging, 2019
To assess the ability of diffusion-weighted imaging (DWI) in predicting the overall survival in p... more To assess the ability of diffusion-weighted imaging (DWI) in predicting the overall survival in patients who underwent Yttrium 90 radioembolization (90 Y-RE) for colorectal liver metastases (CLM) with other well-established clinical and imaging parameters by comparing the pre-and post-treatment apparent diffusion coefficient (ADC) values of the lesions. Methods: A total of 81 metastatic lesions of 27 consecutive patients who underwent DWI before and after the 90 Y-RE session were enrolled in the study. ADC values were calculated from the entire (ADC e) and peripheral (ADC p) tumor on pre-and post-treatment DWI, and any relative increase in ADC > 0% accepted as a functional imaging response. The impact of functional imaging response in addition to other well-known parameters including Response Evaluation Criteria in Solid Tumors (RECIST), hepatic tumor burden, Eastern Cooperative Oncology Group performance status (ECOG-PS) and the presence of extrahepatic metastases in predicting overall survival (OS) was assessed using Kaplan-Meier curves and Cox-regression analyses. Results: The median OS of the patients was 10 months (range, 6-20 months) while the median OS of the responders being significantly longer than the non-responders for ADC e and ADC p (median 11 vs 7 months, P = 0.003; median 12 vs. 7 months, P < 0.0001, respectively). The RECIST score was also significantly affected the OS (progressive or stable disease median 8 months vs. partial response 15 indent months, P = 0.019). The other parameters including hepatic tumor burden, gender, ECOG score, the involvement of the liver lobes, and the presence of extrahepatic metastases were not associated with the OS. In multivariate analysis, only ADC p remained as an independent predictor of OS (P = 0.003, HR = 19.878). Conclusion: Any increase in relative ADC p or ADC e values after Y90-RE treatment was associated with longer OS in CLM patients, and DWI seems to be valuable imaging biomarker in predicting OS in CLM patients during the early post-interventional period after 90 Y-RE.
Nuclear Medicine Seminars, 2018
Metastatik ve kastrasyona dirençli prostat kanseri (mKDPK) tedavisinde son yıllarda ciddi gelişme... more Metastatik ve kastrasyona dirençli prostat kanseri (mKDPK) tedavisinde son yıllarda ciddi gelişmeler olmaktadır. Yeni geliştirilen ilaçların da etkisiyle (örneğin; Enzalutamide, abiraterone) mKDPK'de sağkalım süreleri her geçen yıl artış göstermektedir. Ancak yeni nesil tedavi seçeneklerine 1-2 yıl içerisinde direnç gelişmekte ve bu aşamadan sonra sağkalım süreleri belirgin olarak kısalmaktadır (1). Bu grup hastalarda ise Ra-223 ve Lu-177 prostat spesifik membran antijeni (PSMA) tedavilerinin kullanımı her geçen gün artmaktadır (2,3). PSMA diğer adı glutamat karboksipeptidaz II olan ve hücre içerisinde enzim fonksiyonları bulunan bir transmembran glikoproteindir ve yaklaşık 30 yıl kadar önce bulunmuştur. Folat'ın hücre içine alınmasında rolü olduğu gibi hücre migrasyonu, hücre sağkalım ve proliferasyonunda da görev alır. Sağlıklı prostat epitel hücrelerinde düşük düzeyde ekspresyonu bulunmakla birlikte prostat kanserinde 1000 kata varan oranlarda daha fazla bulunabilmektedir (4). Bu durum PSMA molekülünü prostat kanseri tanı ve tedavisinde radyofarmasötikler için hedef haline Metastatik ve kastrasyona dirençli prostat kanseri tedavisinde Lu-177 prostat spesifik membran antijeni (PSMA) tedavisi son yıllarda başarı ile uygulanmaya başlamış ve hızla yaygınlaşmıştır. Lu-177 PSMA tedavisi belirgin ağrı palyasyonu ve hasta performans skorlarında artış sağlarken, %44-60 oranlarında serum prostat spesifik antijen (PSA) seviyelerinde >%50 düşüş bildirilmiştir. Retrospektif serilerin meta-analizine göre 3. basamak sistemik tedavi seçeneklerinden daha uzun sağkalım ve daha yüksek oranda PSA yanıtları elde edilmektedir. Bu sonuçlara ise kontrol edilebilir bir yan etki profili ile ulaşılmaktadır. Bu derlemede Lu-177 PSMA tedavisinin hangi hasta gruplarında, ne zaman, hangi dozlarda uygulanacağından bahsedilecek olup tedavinin pratik uygulama yönleri, tedavi yanıtları ve yan etkileri tartışılacaktır.
Nuclear Medicine Communications, 2018
Purpose The intensity of prostate-specific membrane antigen (PSMA) expression increases as the tu... more Purpose The intensity of prostate-specific membrane antigen (PSMA) expression increases as the tumor grade increases and the uptake of Ga-68-PSMA is higher in highgrade tumors. The aim of the present study was to evaluate the correlation of preoperative tracer uptake of primary tumor to Gleason Score in patients who underwent prostatectomy. Patients and methods We retrospectively evaluated 141 patients who had Ga-68-PSMA positron emission tomography/computed tomography (PET/CT) imaging and who underwent prostatectomy. All patients had a diagnosis of prostate cancer on the basis of 10-24 cores transrectal ultrasound-guided biopsy (TRUS-Bx). Histological assessment was performed according to the New Contemporary Prostate Cancer Grading System. All patients had a prostate-specific antigen (PSA) level measurement within maximum of 28 days before Ga-68-PSMA PET/CT. Region of interests were drawn manually around the prostate gland, avoiding the bladder activity, to calculate the maximum standardized uptake values (SUVmax) values. Results The median PSA values for all patients were 10.0 ng/ml. PSA values for low-risk patients were significantly lower than those of high-risk patients (P < 0.001). There were 41.1% upgrades and 7.8% downgrades following prostatectomy in terms of Grade Groups. According to the final pathology reports, 21% (n = 16) of patients moved from a low-risk level (grade groups 1 + 2) to a high-risk level (grade groups 3 + 4 + 5). The median SUVmax value was 8.8, ranging from 2.1 to 62.4. There was a strong correlation between SUVmax values and grade groups (Pearson ρ = 0.66) (P < 0.001). The mean SUVmax values of high-risk patients were significantly higher than those of low-risk patients (18.9 ± 12.1 vs. 7.16 ± 6.2, respectively) (P < 0.001). Receiver operation characteristic curve analysis of SUVmax at the cutoff value of 9.1 showed a high sensitivity (78%) and specificity (81%) for detection of high risk disease. Conclusion SUVmax values correlate significantly with the grade groups of the primary tumor. The intraprostatic accumulation sites may predict clinically significant cancer and potentially serve as a target for biopsy sampling in conjunction with mpMRI in selected patients. Nucl Med Commun 40:86
Radiation and environmental biophysics, Jan 8, 2018
The aim of the present study was to review the available models developed for calculating red bon... more The aim of the present study was to review the available models developed for calculating red bone marrow dose in radioiodine therapy using clinical data. The study includes 18 patients (12 females and six males) with metastatic differentiated thyroid cancer. Radioiodine tracer of 73 ± 16 MBq I was orally administered, followed by blood sampling (2 ml) and whole-body scans (WBSs) done at several time points (2, 6, 24, 48, 72, and ≥ 96 h). Red bone marrow dose was estimated using the OLINDA/EXM 1.0, IDAC-Dose 2.1, and EANM models, the models developed by Shen and co-workers, Keizer and co-workers and Siegel and co-workers, and Traino and co-workers, as well as the single measurement model (SMM). The results were then compared to the standard reference model Revised Sgouros Model (RSM) reported by Wessels and co-workers. The mean dose deviations of the Traino, Siegel, Shen, Keizer, OLINDA/EXM, EANM, SMM, and IDAC-Dose 2.1 models from the RSM were - 17%, - 24%, 6%, - 29%, - 15%, 40%, 4...
Nuclear medicine communications, 2018
The development of reliable dosimetry models promotes the individualized therapy concept toward m... more The development of reliable dosimetry models promotes the individualized therapy concept toward more success and less complications. This paper evaluates the traditional maximum empirical activity (250 mCi) and the benefit of joining two dosimetry approaches to optimize the therapeutic activity and radioiodine efficacy in metastatic differentiated thyroid cancer. Nineteen (12 females and seven males) patients with metastatic differentiated thyroid cancer were included in the present study. The mean age of the patients was 46±16 years. The mean height and weight were 1.67±0.11 m and 76±18 kg, respectively. Radioiodine treatment was given by recombinant human thyrotropin stimulation in seven patients, and thyroxine withdrawal was successful for the rest 12 patients. The mean thyroid-stimulating hormone value was 68±34 μIU/ml, and the mean thyroglobulin value was 408±356 ng/ml before therapy. After radiotracer administration, lesion-absorbed dose was calculated in addition to red marro...
Malecular Imaging and Radionuclide Therapy, 2017
Objective: The aim of the study was to estimate the radiation-absorbed doses and to study the in ... more Objective: The aim of the study was to estimate the radiation-absorbed doses and to study the in vivo and in vitro stability as well as pharmacokinetic characteristics of lutetium-177 (Lu-177) prostate-specific membrane antigen (PSMA)-617. Methods: For this purpose, 7 patients who underwent Lu-177-PSMA therapy were included into the study. The injected Lu-177-PSMA-617 activity ranged from 3.6 to 7.4 GBq with a mean of 5.2±1.8 GBq. The stability of radiotracer in saline was calculated up to 48 h. The stability was also calculated in blood and urine samples. Post-therapeutic dosimetry was performed based on whole body and single photon emission computed tomography/computed tomography (SPECT/CT) scans on dualheaded SPECT/CT system. Results: The radiochemical yield of Lu-177-PSMA-617 was >99%. It remained stable in saline up to 48 h. Analyses of the blood and urine samples showed a single radioactivity peak even at 24 hours after injection. Half-life of the distribution and elimination phases were calculated to be 0.16±0.09 and 10.8±2.5 hours, respectively. The mean excretion rate was 56.5±8.8% ranging from 41.5% to 65.4% at 24 h. Highest radiation estimated doses were calculated for parotid glands and kidneys (1.90±1.19 and 0.82±0.25 Gy/GBq respectively). Radiation dose given to the bone marrow was significantly lower than those of kidney and parotid glands (p<0.05) (0.030±0.008 Gy/GBq). Conclusion: Lu-177-PSMA-617 is a highly stable compound both in vitro and in vivo. Lu-177-PSMA-617 therapy seems to be a safe method for the treatment of castration-resistant prostate cancer patients. The fractionation regime that enables the longest duration of tumor control and/or survival will have to be developed in further studies.
Nuclear Medicine Communications, 2017
Objective Prediction and early diagnosis of orbitopathy is needed in patients with Graves' diseas... more Objective Prediction and early diagnosis of orbitopathy is needed in patients with Graves' disease, especially when radioiodine therapy is planned. Positron emission tomography/computerized tomography (PET/CT) using flourine-18-fluorodeoxyglucose (FDG) is an effective imaging modality in detection of inflammation, however, its ability to detect orbital inflammation has not been well studied. The aim of our study is to determine the ability of FDG PET/CT to detect orbital inflammation related with Graves' disease, identify active orbitopathy, predict the radioiodine-triggered orbitopathy, and find out the effects of radioiodine on orbital inflammation. Materials and methods Total 31 Graves' disease patients and 17 controls were included. All Graves' disease patients underwent cranial FDG PET/CT imaging prior therapy. Radioiodine therapy and post-treatment PET/CT study was applied to 21 patients. PET/CT images of all examinees were evaluated, measuring extraocular muscle maximum standard uptake value (SUV max) and muscle thickness. Results FDG uptake was increased in the majority of extraocular muscles in Graves' disease patients in comparison to controls and this increase was found to be irrelevant from muscle thickness. Extraocular muscle SUV max values did not increase in Graves' orbitopathy patients who received radioiodine under corticosteroid prophylaxis. SUV max level of all orbital rectus muscles were increased after radioiodine therapy in nonsmokers, whereas no increase was detected in smokers. Conclusion FDG PET/CT may be helpful in detection of extraocular muscle inflammation and it may show ongoing orbitopathy in early stages of inflammation before anatomical changes occur. Nucl Med Commun
European journal of nuclear medicine and molecular imaging, Jan 18, 2017
To assess the diagnostic accuracy of (68)Ga-PSMA PET in predicting lymph node (LN) metastases in ... more To assess the diagnostic accuracy of (68)Ga-PSMA PET in predicting lymph node (LN) metastases in primary N staging in high-risk and very high-risk nonmetastatic prostate cancer in comparison with morphological imaging. This was a multicentre trial of the Society of Urologic Oncology in Turkey in conjunction with the Nuclear Medicine Department of Cerrahpasa School of Medicine, Istanbul University. Patients were accrued from eight centres. Patients with high-risk and very high-risk disease scheduled to undergo surgical treatment with extended LN dissection between July 2014 and October 2015 were included. Either MRI or CT was used for morphological imaging. PSMA PET/CT was performed and evaluated at a single centre. Sensitivity, specificity and accuracy were calculated for the detection of lymphatic metastases by PSMA PET/CT and morphological imaging. Kappa values were calculated to evaluate the correlation between the numbers of LN metastases detected by PSMA PET/CT and by histopath...
Nuclear Medicine Communications, 2017
Introduction Prostate-specific membrane antigen (PSMA) is increasingly being recognized as a nove... more Introduction Prostate-specific membrane antigen (PSMA) is increasingly being recognized as a novel target for the PET imaging of prostate cancer (PCa) and 68 Ga-DKFZ-11 (68 Ga-PSMA) has been suggested as a novel tracer for detection of PCa relapses and metastases. The aim of this study was to evaluate the diagnostic value of PSMA PET/CT in the diagnosis of recurrent PCa with low prostate-specific antigen (PSA) levels. Patients and methods We carried out a retrospective analysis of patients who underwent PSMA PET/CT from November 2013 to December 2014 in our department. Among these patients, 50 out of 178 who had increasing PSA levels (< 5 ng/ml) and did not have known metastasis were included in this study. Results Patients had an average PSA of 1.41 ng/ml. A total of 29 patients (58%) showed at least one positive lesion. PET positivity rates of 31% (n = 4), 54% (n = 13), and 88% (n = 14) were observed in patients with a PSA level of less than 0.2, 0.2-2, and 2-5 ng/ml, respectively. A positive correlation was observed between positivity rate and Gleason scores and blood PSA levels. Verification was performed in 46 patients, with biopsy (n = 3) and follow-up, and conventional imaging studies at the time of the PET/CT or during follow-up with a mean period of 10.6 ± 3.3 months and ranged from 3.8 to 16.4 months. According to patientbased analysis of 46 cases, 57% of patients had true positive, 24% of patients had true negative, 2% of patients had false positive, an 18% of patients had false-negative findings. A sensitivity of 76.47% (95% confidence interval: 58.83-89.25%) and a specificity of 91.67% (95% confidence interval: 61.52-99.79%) were found. Conclusion PET/CT with 68 Ga-PSMA is a valuable tool for assessing recurrence of PCa with a high sensitivity in patients who have PSA levels between 0.2 and 5 ng/ml. In addition, this study suggests that PSMA PET/CT can be used in patients with very low (< 0.2 ng/ml) but increasing PSA levels, which, in many cases, may influence further clinical management.