Comparison of planned and measured rectal dose in-vivo during high dose rate Cobalt-60 brachytherapy of cervical cancer (original) (raw)
Related papers
Journal of Radiation Oncology, 2020
Objective The objective of this study was to compare the ICRU 38 calculated rectal dose with in vivo dosimetry measured doses in cobalt-60 HDR brachytherapy for cervical cancer. Methods A total of 48 brachytherapy insertions done on 15 patients treated from January to March 2017 at our institution were included in this prospective cross-sectional study. Results The results demonstrated no significant difference between the computed ICRU rectal point dose and in vivo maximum measured rectal dose ((r) 0.6208, p < 0.0001 [S]; t test p = 0.1578 [NS] 95% CI − 0.78 to 0.46), but a significant difference between ICRU rectal point and in vivo mean measured rectal dose ((r) 0.6033, p < 0.0001 [S]; t test p < 0.0001 [S] 95% CI − 0.81 to 0.35). These findings were seen even when sub-analyzed for the two used fraction sizes of 7 Gy and 8 Gy. The results also showed no significant differences in the maximum ((r) 0.9029, p < 0.0001 [S]; t test p = 0.2576 [NS], 95% CI − 0.21 to 0.06) and mean ((r) 0.9766, p < 0.0001 [S]; t test p = 0.2786 [NS], 95% CI − 0.93 to 0.03) doses taken from treatment planning system assigned dose points coinciding with the imaged probes of the in vivo dosimeter. Conclusion Overall, this study was able to provide additional evidence that in vivo dosimetry can be validly used in the clinical setting to estimate the dose to the rectum during Co-60 HDR brachytherapy. Use of this technique allows for an additional quality assurance method that can contribute to reductions of errors in dose delivery.
Polish Journal of Medical Physics and Engineering, 2020
Transition from low dose rate brachytherapy to high dose rate brachytherapy at our department necessitated the performance of dose verification test, which served as an end-to-end quality assurance procedure to verify and validate dose delivery in intracavitary brachytherapy of the cervix and the vaginal walls based on the Manchester system. An in-house water phantom was designed and constructed from Perspex sheets to represent the cervix region of a standard adult patient. The phantom was used to verify the whole dose delivery chain such as calibration of the cobalt-60 source in use, applicator, and source localization method, the output of treatment planning with dedicated treatment planning system, and actual dose delivery process. Since the above factors would influence the final dose delivered, doses were measured with calibrated gafchromic EBT3 films at various points within the in-house phantom for a number of clinical implants that were used to treat a patient based on depar...
Clinical Medicine Insights: Oncology, 2010
is widely used for high-dose rate brachytherapy. Co-60 source with similar geometric and dosimetric properties are now available. It has a longer half life but higher energy than Iridium-192. If Co-60 source can produce similar results, it will be more economical for low resource settings. Objective: To evaluate the acute gastrointestinal and genitourinary toxicity associated with Co-60 source in the brachytherapy of cervical cancer. Methods: Seventy patients with cervical cancer received 45 Gy in 22 fractions of pelvic external beam radiotherapy and 19.5 Gy in 3 fractions of HDR with Co-60 source using tandem and ring applicators with 6 courses of cisplatin 50 mg/m 2 and 5 fluorouracil 1000 mg/m 2 Results: The median total BED (Gy 10 ) for tumor was 86.2 (84.4-88.8) while that for rectum (BED Gy 3 ) was 124.4 (120-133). Two patients (3%) had grade 3 gastrointestinal toxicity while all others had #grade 2 toxicity and this is comparable with previous results. Conclusion: Co-60 as HDR brachytherapy source is tolerable and is economical for low resource settings. every 3 weeks Toxicity was scored using NCI-CTC version 4.0. ntekim et al 90 Clinical Medicine Insights: Oncology 2010:4
Journal of Contemporary Brachytherapy
Purpose: To record and report dosimetric and clinical outcomes of interstitial brachytherapy using cobalt-60 (60 Co) source in cervical cancer. Material and methods: Seventy patients who underwent external beam radiotherapy with dose of 45 Gy in 25 fractions, followed by interstitial brachytherapy (ISBT) 6.5 Gy × 4 fractions were included into this study. The ISBT applicators were inserted under combined spinal and epidural anesthesia. Computed tomography (CT) simulation was performed and axial CT images were transferred to treatment planning system. High-risk clinical target volume (CTV HR) and organs at risks (OARs) were contoured. Four fractions of 6.5 Gy were prescribed to CTV HR using inverse planning technique. Patients were followed-up for 3 years. Dosimetric parameters and clinical outcomes were recorded and compared with available literature. Results: Seventy patients with FIGO stage IIB-IVA were included in the study. The median EQD 2 of 2 cm 3 of bladder, rectum, sigmoid and D 90 CTV HR were 70 Gy (53-75 Gy), 64 Gy (51-71 Gy), 48 Gy (44-72 Gy), and 77 Gy (70-86 Gy), and dose homogeneity index (DHI), dose non-uniformity ratio (DNR), coverage index (CI), overdose volume index (OI), and conformal index (COIN) were 0.
is widely used for high-dose rate brachytherapy. Co-60 source with similar geometric and dosimetric properties are now available. It has a longer half life but higher energy than Iridium-192. If Co-60 source can produce similar results, it will be more economical for low resource settings. Objective: To evaluate the acute gastrointestinal and genitourinary toxicity associated with Co-60 source in the brachytherapy of cervical cancer. Methods: Seventy patients with cervical cancer received 45 Gy in 22 fractions of pelvic external beam radiotherapy and 19.5 Gy in 3 fractions of HDR with Co-60 source using tandem and ring applicators with 6 courses of cisplatin 50 mg/m 2 and 5 fluorouracil 1000 mg/m 2 Results: The median total BED (Gy 10 ) for tumor was 86.2 (84.4-88.8) while that for rectum (BED Gy 3 ) was 124.4 (120-133). Two patients (3%) had grade 3 gastrointestinal toxicity while all others had #grade 2 toxicity and this is comparable with previous results. Conclusion: Co-60 as HDR brachytherapy source is tolerable and is economical for low resource settings. every 3 weeks Toxicity was scored using NCI-CTC version 4.0. ntekim et al 90 Clinical Medicine Insights: Oncology 2010:4
Variability of Marker-Based Rectal Dose Evaluation in HDR Cervical Brachytherapy
Medical Dosimetry, 2010
In film-based intracavitary brachytherapy for cervical cancer, position of the rectal markers may not accurately represent the anterior rectal wall. This study was aimed at analyzing the variability of rectal dose estimation as a result of interfractional variation of marker placement. A cohort of five patients treated with multiple-fraction tandem and ovoid high-dose-rate (HDR) brachytherapy was studied. The cervical os point and the orientation of the applicators were matched among all fractional plans for each patient. Rectal points obtained from all fractions were then input into each clinical treated plan. New fractional rectal doses were obtained and a new cumulative rectal dose for each patient was calculated. The maximum interfractional variation of distances between rectal dose points and the closest source positions was 1.1 cm. The corresponding maximum variability of fractional rectal dose was 65.5%. The percentage difference in cumulative rectal dose estimation for each patient was 5.4%, 19.6%, 34.6%, 23.4%, and 13.9%, respectively. In conclusion, care should be taken when using rectal markers as reference points for estimating rectal dose in HDR cervical brachytherapy. The best estimate of true rectal dose for each fraction should be determined by the most anterior point among all fractions.
Journal of Contemporary Brachytherapy
Purpose: Brachytherapy (BRT) is a cornerstone in cervical cancer treatment, with the ultimate goal to maximize the tumor dose while sparing organs at risk (OARs), such as rectum. Several studies evaluated the effect of rectal volume on rectal doses, but the results are inconsistent. This study aimed to evaluate the rectal volume and dose-volume histogram (DVH) relationship in high-dose-rate (HDR) brachytherapy in locally advanced cervical cancer. Material and methods: Planning computed tomography of 65 patients who underwent HDR brachytherapy boost as a component of definitive radiotherapy from March 2016 to February 2018 were reviewed. OARs and target volume were re-delineated by a single physician to decrease interobserver variation. Two sets of plan were generated; in the first set, the dose was prescribed to point A with Manchester system loading pattern, while in the second set, the dose was prescribed to high-risk clinical target volume (HR-CTV) D 90 with inverse planning optimization. The DVH values for rectum, sigmoid, and HR-CTV were generated and correlated with rectal or sigmoidal volume variation. Results: Dose to 2cc (D 2cc), 1cc (D 1cc), and 0.1cc (D 0.1cc) of rectum and sigmoid showed a significant decrease in optimization vs. point A planning (p < 0.0001). HR-CTV D 90 coverage was significantly higher in optimization vs. point A planning (p = 0.041). Rectal volume showed a significant correlation with D 2cc (rs, 0.302, p = 0.014), D 1cc (rs, 0.310, p = 0.012), and D 0.1cc (rs, 0.283, p = 0.02) of rectum in optimization planning. Conclusions: Larger rectal volumes are associated with higher rectal dose parameters during HDR brachytherapy using inverse planning optimization. This method spares OAR, while producing reasonable HR-CTV D 90. Prospective studies are needed to find appropriate technique of rectal volume reduction.
International Journal of Radiation Oncology*Biology*Physics, 2010
Purpose: To evaluate the predictive factors for rectal dose of the first fraction of high-dose-rate intracavitary brachytherapy (HDR-ICBT) in patients with cervical cancer. Methods and Materials: From March 1993 through February 2008, 946 patients undergoing pelvic irradiation and HDR-ICBT were analyzed. Examination under anesthesia (EUA) at the first implantation of the applicator was usually performed in the early period. Rectal point was determined radiographically according to the 38th Report of the International Commission of Radiation Units and Measurements (ICRU). The ICRU rectal dose (PRD) as a percentage of point A dose was calculated; multiple linear regression models were used to predict PRD. Results: Factors influencing successful rectal dose calculation were EUA (p < 0.001) and absence of diabetes (p = 0.047). Age (p < 0.001), body weight (p = 0.002), diabetes (p = 0.020), and EUA (p < 0.001) were independent factors for the PRD. The predictive equation derived from the regression model was PRD (%) = 57.002 + 0.443 Â age (years) À 0.257 Â body weight (kg) + 6.028 Â diabetes (no: 0; yes: 1) À 8.325 Â EUA (no: 0; yes: 1) Conclusion: Rectal dose at the first fraction of HDR-ICBT is positively influenced by age and diabetes, and negatively correlated with EUA and body weight. A small fraction size at point A may be considered in patients with a potentially high rectal dose to reduce the biologically effective dose if the ICRU rectal dose has not been immediately obtained in the first fraction of HDR-ICBT. Ó
Biologically effective doses in medium dose rate brachytherapy of cancer of the cervix
Radiation Oncology Investigations, 1997
The amount of dose reduction on changing from low dose rate (LDR) brachytherapy to medium dose rate (MDR) or high dose rate (HDR) afterloading has been the subject of much debate. The magnitude of reduction depends, together with other possible factors, on two radiobiological parameters: the ␣/ ratio and the half-time of repair of the relevant tissues. In an attempt to extract these radiobiological parameters for the late rectal complications observed in our previously published clinical results four different schedules using MDR and one using LDR are analyzed. The percentage incidence of complications was a function of increasing biologically effective dose (BED), but would yield nonsense scattergrams if plotted against raw total dose. In addition, for three other published MDR series, three LDR series, and two HDR series, the incidence of rectal complications is plotted against BED to examine the predictive potential of using BED as the surrogate of total dose. Our own results were published in 1996, consisting of 102 patients treated at the LDR of 0.44 Gy/hr and 88 patients treated by four different schedules using an MDR of 1.6-1.7 Gy/hr. Follow-up is at least 3 years in all schedules. The linear quadratic formula including the ''g'' dose rate factor was used to analyze them, assuming exponential repair of the repairable beta term. First, multivariate and profilelikelihood analyses were carried out to obtain estimates of ␣/ and T 1 ⁄2 for rectal lateresponding tissues. Then graphs of incidence of rectal complications vs. BED were constructed, assuming ␣/ = 3 Gy and T 1 ⁄2 = 1.5 hr, values which had not been contradicted by the multivariate analysis. Graphs were drawn both for ''all grades including mild reactions'' (grades 1 + 2 + 3) and for ''serious'' complications (grade 3 in our system). In addition, other published cervical brachytherapy series were reviewed, with calculation of their BEDs if not published by the authors. It was necessary to review and compare their grading systems, so that ''mild and moderate'' (grades 1 and 2) could be contrasted with ''serious'' (grades 3 and 4 or 5 in various systems). Comparisons were made with other published results, including three LDR, three MDR, and two HDR series spanning from 1982 to 1997. The BEDs at which the incidence of rectal complications rose above the arbitrary level of 10% were compared for all three ranges of dose rate. The multivariate analysis gave estimates of ␣/ and T 1 ⁄2 which were not significantly different from 3 Gy and 1.5 hr, respectively, so these values were used to compute the BEDs for the subsequent comparisons. It was found that the graphs of incidence of rectal complications for ''all grades including mild'' agreed rather better between all series than might have been expected, within a provisional (10%) threshold BED of range 100-123 Gy 3 (60-74 Gy given as 2 Gy fractionated external beam or as LDR). The dose-response curves di-verged above these values, as expected until common grading systems such as SOMA/ LENT become more widely used. For ''serious'' complications the 10% incidence occurred at a median BED of 140 Gy 3 (84 Gy given as 2 Gy fractionated external beam or as LDR), range 124-155 Gy 3 . The use of BED (or extrapolated response dose), assuming ␣/ = 3 Gy and T 1 ⁄2 = 1.5 hr, instead of total dose, enabled incidence of late rectal complications in cervical brachytherapy with LDR, MDR, and HDR to be plotted in a reasonably consistent way. This does not mean that those parameter values have been definitively determined, but they appear to be provisional values that may be of use in comparing the expected effects of new schedules until better values are obtained from greater use of common grading systems.