759 Re-Implant: A Therapeutical Option in Case of Inadequate Post-Implant Dosimetry After Permanent Prostate Brachytherapy (original) (raw)

Importance of Post-Implant Dosimetry in Permanent Prostate Brachytherapy

European Urology, 2002

Objective: Post-implant dosimetry has become the gold standard for implant evaluation and it is recommended that it be performed on all patients undergoing prostate brachytherapy. The technique, results and correlation with clinical outcomes will be presented. Methods: The method and outcomes of post-implant dosimetry are explored by outlining the experience at the Mount Sinai Medical Center, New York, as well as reviewing the literature. The most accurate time to perform postimplant dosimetry is 1 month after implant. Computed tomography (CT)-based dosimetry is currently the best available technique for performing this analysis. The technique involves taking 3-mm abutting CT slices throughout the implanted area. The prostate and normal structures are outline on the CT slices. These structures are recreated in three dimensions. Dose volume histograms (DVH) are created and allow the dose to these organs to be quanti®ed. Results: The relationship between dosimetric ®ndings and clinical outcomes has been established. The dose delivered to 90% of the prostate on DVH (D90) has been correlated to prostate-speci®c antigen (PCA) control and post-treatment biopsy results. D90 values of 140 Gy have been associated with improved biochemical control and lower positive post-treatment biopsy results. Doses derived from the dosimetric analysis to prostate, urethra and rectum have been correlated with the development of acute and chronic urinary morbidity, sexual potency and rectal morbidity. Future initiatives involve performing dosimetric calculations intraoperatively at the time of the implant. Conclusions: Post-implant CT-based dosimetry is an essential component of prostate brachytherapy. It is the only method of assessing the actual dose delivered to the prostate and normal surrounding structures. Future development in post-implant and intraoperative dosimetry will continue to improve permanent prostate brachytherapy as a safe an effective treatment for prostate cancer. # 2002 Published by Elsevier Science B.V.

Clinical Investigations Case series analysis of post-brachytherapy prostate edema and its relevance to post-implant dosimetry. Post-implant prostate edema and dosimetry

Journal of Contemporary Brachytherapy, 2012

Purpose: We evaluated the post-operative pattern of prostate volume (PV) changes following prostate brachytherapy (PB) and analyzed variables which affect swelling. Material and methods: Twenty-nine patients treated with brachytherapy (14) or combined brachytherapy and external beam radiotherapy modality (15) underwent pre-and post-implant computed tomography (CT). Prostate volume measurements were done on post-operative days 1, 9, 30, and 60. An observer performed 139 prostate volume (PV) measurements. We analyzed the influence of pre-implant PV, number of needles and insertion attempts, number and activity of seeds, Gleason score, use of hormonal therapy and external beam radiation therapy on the extent of edema. We computed a volume correction factor (CF) to account for dosimetric changes between day 1 and day 30. Using the calculated CF, the dose received by 90% (D 90) of the prostate on day 30 (D 90 Day30) was obtained by dividing day 1 (D 90 Day1) by the CF. Results: The mean PV recorded on post-operative day 1 was 67.7 cm 3 , 18.8 cm 3 greater than average pre-op value (SD 15.6 cm 3). Swelling returned to pre-implant volume by day 30. Seed activity, treatment modality, and Gleason score were significant variables. The calculated CF was 0.76. After assessment using the CF, the mean difference between estimated and actual D 90 Day30 was not significant. Conclusions: We observed maximum prostate size on post-operative day 1, returning to pre-implant volume by day 30. This suggests that post-implant dosimetry should be obtained on or after post-operative day 30. If necessary, day 30 dosimetry can be estimated by dividing D 90 Day1 by a correction factor of 0.76.

Significant Underdosage of the Prostate Base after 125-I Brachytherapy on Day 1 Post-implant Dosimetry

International Journal of Radiation Oncology*Biology*Physics, 2009

migration, or OR procedure time were seen. No seed drift greater than 10 mm outside the "packet" of other seeds was seen in the Anchorseed cohort. Conclusions: This report is the first to show the unique "fixity" of AnchorSeedÔ to remain in position after deployment from the Mick applicator. Minimizing seed drag can reduce dose to the penile bulb, and maximize radiation coverage to the apex of the gland.

125I reimplantation in patients with poor initial dosimetry after prostate brachytherapy

International Journal of Radiation Oncology*Biology*Physics, 2004

Purpose: In this case report, we describe 7 patients with suboptimal dosimetry after 125 I prostate brachytherapy who underwent a second implant procedure to improve the dosimetric coverage of the prostate. Methods and Materials: Seven patients underwent second 125 I implants for suboptimal dosimetry after their initial implant for prostate cancer. The pretreatment characteristics (clinical stage, Gleason score, initial prostate-specific antigen level, location of positive cores, International Prostate Symptom Score, potency, use of androgen suppression, initial implant planning characteristics) were noted. The "Day 30" CT-based dosimetry parameters after the first implant and "Day 0" CT-based dosimetry after the reimplant were recorded (volumes of prostate and rectum covered by 100% and 150% of the dose and dose covering 90% of the prostate volume). The toxicity of the second procedure, International Prostate Symptom Scores before and after reimplantation, the clinical course, and prostate-specific antigen outcomes after reimplant were examined. We described our reimplant planning and intraoperative procedure. Results: In all 7 patients, we were able to achieve very favorable dosimetry after the second procedure. The acute toxicity of the reimplant procedure was reasonably low, and the short-term prostate-specific antigen outcome has been favorable. Conclusion: It is possible to add more seeds safely to the dosimetrically cool area after the initial brachytherapy procedure and achieve excellent postimplant dosimetry with acceptable acute toxicity. The ultimate benefits and long-term toxicity of reimplantation are unknown.

Prostate brachytherapy in patients with prostate volumes ≥ 50 cm3: dosimetic analysis of implant quality

International Journal of Radiation Oncology*Biology*Physics, 2000

Objectives: Permanent implantation with 125 I in patients with localized prostate cancer who have prostate volumes > 50 cm 3 is often technically difficult owing to pubic arch interference. The objective of this study was to describe dosimetry outcomes in a group of patients who were implanted using the real-time ultrasound-guided technique who had prostate volumes > 50 cm 3. Materials and Methods: A total of 331 patients received an 125 I prostate seed implant from January 1, 1995, to June 1, 1999, of whom 66 (20%) had prostate volumes > 50 cm 3 at the time of the procedure. The real-time seed implant method was used in all patients and consisted of intraoperative planning and real-time seed placement using a combination of axial and sagittal ultrasound imaging. Pubic arch interference was managed using an extended lithotomy position or by angling the tip of the ultrasound probe in an anterior direction. No preimplant pubic arch CT scan study was performed and no patients were excluded from treatment because of prostate size. Implant quality was assessed using CT-based dosimetry performed 1 month postimplant. Dose-volume histograms for the prostate, bladder, rectum, and urethra volumes were generated. The target dose for these implants was 160 Gy and an adequate implant was defined as the dose delivered to 90% of the prostate (D90) > 140 Gy. The dose delivered to 95% of the prostate (D95) and doses to 30% of the rectal (DRECT30) and urethral (DURE30) volumes were also calculated. Results: Prostate volumes in the 66 patients ranged from 50 to 93 cm 3 (median 57, mean 61 cm 3). Total activity implanted was 27.8-89.1 mCi (median 57 mCi), with a range in activity per seed of 0.36-0.56 mCi (median 0.4 mCi). The prostate D90s and D95s ranged from 13,245 to 22,637 cGy (median 18,750) and 11,856 to 20,853 cGy (median 16,725), respectively. Only one patient (1.5%) had a D90 < 140 Gy. The DURE30 values ranged from 15,014 to 27,800 cGy (median 20,410) and the DRECT30 values were 3137-9910 cGy (median 5515). Conclusion: Implantation of the large prostate can be accomplished using the real-time method. A total of 98.5% of the patients receive a high-quality implant. In addition, these implants should not put patients at increased risk for significant urinary and bowel complications because urethral and rectal doses can be kept at acceptable levels.