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Background: High dose rate (HDR) brachytherapy is commonly used to treat prostate cancer. Existing HDR planning systems solve the dwell time problem for predetermined catheters and a single energy source. Purpose: Additional degrees of freedom can be obtained by relaxing the catheters' pre‐designation and introducing more source types, and may have a dosimetric benefit, particularly in improving conformality to spare the urethra. This study presents a novel analytical approach to solving the corresponding HDR planning problem. Methods: The catheter and dual‐energy source selection problem was formulated as a constrained optimization problem with a non‐convex group sparsity regularization. The optimization problem was solved using the fast‐iterative shrinkage‐thresholding algorithm (FISTA). Two isotopes were considered. The dose rates for the HDR 4140 Ytterbium (Yb‐169) source and the Elekta Iridium (Ir‐192) HDR Flexisource were modeled according to the TG‐43U1 formalism and benchmarked accordingly. Twenty‐two retrospective HDR prostate brachytherapy patients treated with Ir‐192 were considered. An Ir‐192 only (IRO), Yb‐169 only (YBO), and dual‐source (DS) plan with optimized catheter location was created for each patient with N catheters, where N is the number of catheters used in the clinically delivered plans. The DS plans jointly optimized Yb‐169 and Ir‐192 dwell times. All plans and the clinical plans were normalized to deliver a 15 Gy prescription (Rx) dose to 95% of the clinical treatment volume (CTV) and evaluated for the CTV D90%, V150%, and V200%, urethra D0.1cc and D1cc, bladder V75%, and rectum V75%. Dose‐volume histograms (DVHs) were generated for each structure. Results: The DS plans ubiquitously selected Ir‐192 as the only treatment source. IRO outperformed YBO in organ at risk (OARs) OAR sparing, reducing the urethra D0.1cc and D1cc by 0.98% (p=2.22∗10−9$p\ = \ 2.22*{10^{ - 9}}$) and 1.09% (p=1.22∗10−10$p\ = \ 1.22*{10^{ - 10}}$) of the Rx dose, respectively, and reducing the bladder and rectum V75% by 0.09 (p=0.0023$p\ = \ 0.0023$) and 0.13 cubic centimeters (cc) (p=0.033$p\ = \ 0.033$), respectively. The YBO plans delivered a more homogenous dose to the CTV, with a smaller V150% and V200% by 3.20 (p=4.67∗10−10$p\ = \ 4.67*{10^{ - 10}}$) and 1.91 cc (p=5.79∗10−10$p\ = \ 5.79*{10^{ - 10}}$), respectively, and a lower CTV D90% by 0.49% (p=0.0056$p\ = \ 0.0056$) of the prescription dose. The IRO plans reduce the urethral D1cc by 2.82% (p=1.38∗10−4$p\ = \ 1.38*{10^{ - 4}}$) of the Rx dose compared to the clinical plans, at the cost of increased bladder and rectal V75% by 0.57 (p=0.0022$p\ = \ 0.0022$) and 0.21 cc (p=0.019$p\ = \ 0.019$), respectively, and increased CTV V150% by a mean of 1.46 cc (p=0.010$p\ = \ 0.010$) and CTV D90% by an average of 1.40% of the Rx dose (p=8.80∗10−8$p\ = \ 8.80*{10^{ - 8}}$). While these differences are statistically significant, the clinical differences between the plans are minimal. Conclusions: The proposed analytical HDR planning algorithm integrates catheter and isotope selection with dwell time optimization for varying clinical goals, including urethra sparing. The planning method can guide HDR implants and identify promising isotopes for specific HDR clinical goals, such as target conformality or OAR sparing. [ABSTRACT FROM AUTHOR]

Hydrogel spacers (HS) have been widely used in radiotherapy to reduce rectal toxicity while escalating dose for prostate cancer. Saline-filled biodegradable balloon spacers (BS) have been developed and recently introduced for prostate brachytherapy. A retrospective review was performed to compare dosimetry of high-dose-rate brachytherapy (HDR-BT) patients implanted with these spacers. Prostate cancer patients were treated with HDR-BT either without spacer (NS), with HS (SpaceOARTM Hydrogel from Boston Scientific Corp.), or with BS (BioProtect balloon from BioProtect Ltd.) implanted between the prostate and rectum. Eleven patients who underwent whole prostate gland treatment were sampled for each group. Patients who received monotherapy (27-29 Gy in 2 fractions) or combination therapy (15 Gy in 1 fraction + EBRT) were included in this study. The spacer, target, and organs at risk (OAR) including the rectum, bladder, and urethra were contoured on CT and MR images (Fig. 1). The volume and diameter of the spacer were measured. In the treatment plan, target coverage (D90%, V100%, and V150%) and OAR doses (D0.1cc, D1cc, and D2cc , and V75%) between the groups were compared using an unpaired t-test. The median volume of the spacer was 10.6 cc (7.2 - 15.1 cc) for HS and 14.4 cc (10.3 - 16.3 cc) for BS. The median anterior-posterior distance between the prostate and the rectum at the mid-gland was 0.5 cm (0.3 - 0.8 cm) for NS, 1.0 cm (0.7 - 1.4 cm) for HS, and 1.8 cm (1.5 - 2.0 cm) for BS. Similar target coverages (median D90 = 106% (105 - 110%, p = 0.5) for NS, 105% (104 - 108%, p = 0.8) for HS, and 106% (104 - 110%) for BS) were achieved from the three groups. A statistically significantly lower dose to the rectum was observed for BS when compared to NS or HS (median D2cc = 61% (48 - 70%, p < 0.001) for NS, 53% (50 - 67%, p = 0.01) for HS, and 44% (34 - 59%) for BS). No statistical differences in dose to the bladder were observed (median D2cc = 66% (45 - 70%, p =0.08) for NS, 66% (56 - 71%, p = 0.3) for HS, and 68% (58 - 74%) for BS). A statistically significant increase in maximum dose to the urethra was observed with BS when compared to NS and HS (D0.1cc = 107.8% (103.7 - 110.0%, p < 0.001) for NS, 109.7% (107.0 - 109.9%, p = 0.003) for HS, and 110.3% (109.6 - 113.1%) for BS). The use of saline-filled biodegradable BS has the benefit of significantly reducing rectal dose compared to HS while providing the same target dose coverage. However, the filling volume must be carefully determined, as injecting large amounts of saline may deform the prostate and displace implanted catheters close to the urethra, creating hot spots in the urethra. Further studies are necessary to evaluate the impact of these dosimetric differences on clinical outcomes. [ABSTRACT FROM AUTHOR]

Introduction: To identify differences in acute urinary and sexual toxicity between a 6-fraction and 2-fraction high-dose-rate brachytherapy monotherapy regimen and correlate dosimetric constraints to short-term toxicity.Methods: A single institution retrospective study of 116 men with prostate cancer treated with HDR monotherapy from 2010 to 2015 was conducted. Eighty-one men had 7.25 Gy × 6-fractions and 35 men had 13.5 Gy × 2-fractions. Patients had two CT-planned implants spaced 1-2 weeks apart. Patient baseline characteristics, International Prostate Symptom Scores (IPSS) and Sexual Health Inventory for Men (SHIM) scores were collected pre-treatment and 3, 6 and 12 months post-implantation. Mixed effect modelling was undertaken to compare baseline, 1-6 month and 7-12 month scores between groups. Poisson regression analysis was performed to correlate dosimetric constraints with acute toxicity.Results: There was no difference between baseline and post-implantation IPSS scores between 6-fraction and 2-fraction groups. SHIM scores for men treated with 6-fractions had a steeper decline at 1-6 months, but resolved at 7-12 months. Pre-treatment alpha-blocker use correlated with worse short-term acute urinary toxicity. Worsened SHIM score correlated with increasing age, diabetes mellitus and androgen-deprivation therapy. In a dosimetric analysis of outcomes, prostate V150 dose and bladder wall (D01.cc, D1cc, D2cc) dose correlated with increased IPSS score.Conclusion: No increased acute genitourinary or sexual dysfunction has been observed in men when transitioning from 6-fraction to 2-fraction HDR monotherapy. A dosimetric correlation was found between the V150 and bladder wall doses for acute urinary toxicity. Future research should continue to standardize and validate dose constraints for prostate HDR monotherapy patients. [ABSTRACT FROM AUTHOR]

Surgery and radiation therapy are standard treatments for lip cancer. Surgery includes removal of all cancer-related tissue and facial reconstruction (cosmetic and functional) of the lips. Reconstruction procedures are available but give a less satisfactory cosmetic result than brachytherapy. In addition, the use of high-dose-rate brachytherapy (HDR-BT) is now becoming more popular than low-dose-rate (LDR) and pulsed-dose-rate (PDR) BT in the treatment of lip cancer since HDR-BT offers the advantage of optimizing dose distribution by varying dwell times. However, due to the short history of use of HDR-BT, relatively few studies on HDR have been published. Two institutions (Ukraine and USA) reviewed the clinical outcomes of lip cancer patients treated with HDR-BT. An interstitial (IS), surface custom mold (SC), or a combination of IS and SC applicator (IS + SC) was used for treatments based on the depth of tumor invasion. Clinical target volume (CTV) was determined by adding 1 cm to the initial visible lesion (gross tumor volume (GTV)). Brachytherapy prescription dose was 24 Gy in 6 fractions in addition to 45-50 Gy for EBRT. If brachytherapy was use as a monotherapy, 50 Gy in 10 fractions was prescribed. Interstitial technique was considered first because of conformal irradiated volume and treatment accuracy (Fig. 1). Typically, 1 to 3 interstitial tubes have been evaluated as sufficient for the planned volume. Optimal spacing between tubes is 1.1-1.3 cm. During the evaluation and optimization of the treatment plan, if adding one or more catheters superficially helped the dose distribution and coverage, one or two additional catheters were added for IS+SC. For tumors less than 5mm deep, SCs were created manually or 3D-printed and used for treatment. Since some implantations and applicator design were suboptimal, manual or inverse planning followed by graphical optimization was used to meet target coverage goal and OAR constraints. A total of 33 cases of lip cancer from two institutions were treated from 2015 to 2021. The median age of the patients was 63 years (range, 42-85). Sixty percent of the patients were males, and forty percent were females. Three patients underwent immunosuppression after lung transplant. By using TNM staging classification for skin cancer, there were 14 stage I (42.4%), 15 stage II (45.5%), and 4 stage III (12.1%) lip cancers. Thirty-one patients (93.9%) had complete responses to treatment. Only 2 patients (6.1%) displayed local recurrences. Grade 1, 2, and 3 acute toxicities were observed in 30.3%, 51.5%, and 18.2% of patients, respectively. Grade 1, 2, and 3 late toxicities were observed in 39.4%, 21.2%, and 0.0% of cases. Cosmetic results were excellent in 21.2%, good in 54.5%, fair in 18.2%, and poor in 6.1% of patients. HDR Brachytherapy can deliver the most conformal radiation dose to the lip cancers. HDR-BT using IS, SC, or IS + SC is an effective treatment for the lip cancer with good outcomes and cosmetic results. The IS approach provides more heterogeneous and local distribution. The SC applicators provides more uniform dosimetry than the IS technique, but typically has a larger irradiated volume. The SC may be good solution for lip brachytherapy, since it is not invasive. However, it has been rarely used since it is quite difficult to make skin mold applicators to fit the irregular surface of the lip. [ABSTRACT FROM AUTHOR]

Abstract: Background: As high‐dose‐rate (HDR) brachytherapy can preferentially spare normal anatomic structures surrounding the radiation target, we report on our experience using this technique in head and neck cancer reirradiation. Methods: Twenty patients received HDR brachytherapy reirradiation with curative or palliative intent from 2010‐2015. Clinical and toxicity outcomes were recorded. Actuarial outcomes were calculated using Kaplan‐Meier analysis. Results: For curative treatment, actuarial 2‐year rates of local control and overall survival (OS) were 73% and 56%, respectively. Palliatively, a 6‐month local control rate of 65% was seen. Age >70 years was associated with poorer OS (P = .042). Prior salvage resection showed a trend toward improved local control and OS (P = .069 and P = .063, respectively). Thirty‐three percent had grade 3 to 4 late toxicities. Conclusion: Curative‐intent HDR brachytherapy reirradiation can provide excellent local control and encouraging OS. Given the late toxicity rates, patient selection is essential, with particular utility for younger patients or those treated with salvage resection. [ABSTRACT FROM AUTHOR]

Purpose High-dose-rate (HDR) prostate brachytherapy delivers a heterogeneous dose distribution throughout the prostate gland. There is however limited information regarding the spatial distribution of this dose heterogeneity. To this end, we analyzed the magnitude and location of intraprostatic dose heterogeneity in HDR prostate brachytherapy. Methods and Materials Five consecutive prostate cancer patients treated with HDR were analyzed. Based on CT-simulation images, each prostate was divided into three sections (apex, base, and mid-gland). These were further subdivided into eight symmetrical sections to give a total of 24 sections. Dose–volume histograms were analyzed from V100–V200% for these 24 sections comparing the means of individual regions, left vs right, apex vs base vs mid-gland, lateral vs medial, and anterior vs posterior. A separate analysis on dose as a function of individual region volume was also performed. Results Analyses comparing the 24 regions showed a maximum 62% difference (range, 21.9–83.9%) at V130% and 19.9% (1.9–20.8%) at V200%. Seven regions were significantly decreased and one significantly elevated from V130–V180% when compared with the mean. The means for lateral sections were 1.57-fold higher than medial sections from V110–V200% ( p < 0.0001). The dose at the base was significantly higher than the rest of the gland from V120–V200 (V150, 35.6 ± 16.2% vs 20.9 ± 13.1%, p < 0.0001). Conclusions There is significant intra-prostatic dose heterogeneity in prostate HDR brachytherapy. This is most notable in the increased dose to base and lateral portions of the gland. Further studies are needed to determine the impact of heterogeneity on clinical outcomes. [ABSTRACT FROM AUTHOR]

HDR prostate brachytherapy automated catheter preplanning methods in literature are effective, but do not consider the full solution space of feasible catheter trajectories as they are limited by the catheter-first nature of optimizing treatment times based on a fixed catheter implant. Instead, we propose a block optimization system to simultaneously optimizes isotope dwell time and dwell positions via curved treatment catheter trajectory prediction. Our holistic HDR treatment planning algorithm follows an alternating block structure to optimize dwell times, catheter groupings, catheter trajectories, and dwell positions cyclically to produce an implant catheter distribution and associated treatment plan. The dwell time optimization block leverages the fast iterative shrinkage thresholding algorithm (FISTA) to analytically determine optimal isotope dwell times. Catheter groupings were determined via normalized graph cutting to partition (or associate) dwell positions onto individual catheters. Catheter trajectories were determined with 3D spline fitting. Dwell positions were spatially optimized to guarantee that all dwell positions lie on a treatment catheter in the final plan. The four blocks were alternatingly executed to produce a deliverable treatment plan with optimal catheter trajectories for a single retrospective HDR patient. The block-optimized catheter trajectory distribution was evaluated for feasibility, and the plan dose volume histogram (DVH) was compared to the clinical plan. The block-optimized plan dosimetry is comparable to the clinically delivered plan based on manually placed catheters by an expert, as shown in Figure 1a. For the optimized plan, urethra V75 = 2.93cc, bladder V75 = 2.32cc, and rectum V75 = 0cc, compared to urethra V75 = 3.05cc, bladder V75 = 1.83cc, and rectum V75 = 0.17cc for the clinical plan. While there are tradeoffs in the OAR metrics, this is likely due to optimization weighting in the dwell time module and the overall DVH similarity supports the efficacy of our treatment planning system. Further, the predicted curved catheter trajectories shown in Figure 1b appear physically feasible and mimic the clinically popular peripheral loading technique. Our groundbreaking integrative treatment planning system creates clinically feasible treatment plans with optimized curved catheter trajectories. This shows promise as a method for generating better catheter distributions and integrating with novel robotic insertion mechanisms.] [ABSTRACT FROM AUTHOR]

Purpose To report early clinical outcomes of high-dose-rate interstitial image-guided brachytherapy (BT) in the definitive management of locally advanced cervical cancer. Methods We retrospectively analyzed 31 locally advanced cervical cancer patients treated at our institution between January 2010 and April 2013. About 88% had advanced disease based on the International Federation of Gynecology and Obstetrics guidelines, and 87% received concurrent chemotherapy. All patients were treated with external beam radiation therapy to a median dose of 45 Gy (range, 39.6–58 Gy) before receiving BT. High-dose-rate BT was delivered in a single implant to a median dose of 6 Gy × five fractions to a CT-defined volume. Median total equivalent 2-Gy dose, dose covered by 90% of the high-risk clinical target volume (HR-CTV D 90 ), and HR-CTV were 84, 87.4, and 49.9 cc, respectively. Kaplan–Meier method was used for actuarial survival analysis, and toxicity was graded using Common Terminology Criteria for Adverse Events, version 4.0. Results Median followup was 19.3 months. Two-year actuarial local control, regional control, and distant metastasis (DM) were 90%, 93%, and 23.6%, respectively. Two-year disease-free survival was 55%. Genitourinary, gastrointestinal, or gynecologic Grade 3 toxicity was seen in 5 patients (3 T4a and 2 T3b) for crude rates of 13%, 7%, and 3%, respectively. Stratifying HR-CTV by <30 and >30 cc and then by HR-CTV D 90 of <85, 85–90, and >90 Gy showed that 100% of the local failures, regional failures, DM, and G3 toxicity occurred in >30 cc group. The rate of DM was also significantly higher in the >30 cc group ( p = 0.036). Conclusions An interstitial approach can achieve excellent outcomes in cases where intracavitary and/or hybrid approaches are either not suitable or not available. [ABSTRACT FROM AUTHOR]

This retrospective study compares high dose rate brachytherapy (HDR BT) monotherapy against HDR BT and external beam radiation therapy (EBRT), with and without androgen deprivation therapy (ADT), to determine non-inferiority of HDR BT alone in the treatment of unfavorable intermediate risk (UIR) prostate cancer. Data were obtained from two registries from 1991-present. 633 patients with UIR prostate cancer treated with HDR BT were included. Patients who received only HDR BT received 42-45Gy/6 fractions (fx) or 27 Gy/2 fx. For HDR BT+EBRT, the HDR dose was 20-24 Gy/2 fx, 24 Gy/4 fx, or 15 Gy/1 fx. EBRT patients received 45 Gy/25 fx to the prostate +/- pelvic nodal radiation. GU/GI toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. Treatment group differences were assessed via two-sample T test or ANOVA, and associations between categorical variable and treatment group were assessed via chi-squared or Fisher's exact test. Time-to-event analyses were carried out to evaluate relationship between treatments and primary outcome variables. Five primary endpoints were used to assess freedom from biochemical recurrence (FFBC), freedom from distant metastasis (FFDM), freedom from local failure (FFLF), cancer specific survival (CSS), and overall survival (OS). Univariate analysis was conducted using the Kaplan-Meier method and log-rank test to the primary event. For multivariate analysis, Cox proportional hazard (Cox PH) regression and Fine & Gray competing risk regression were carried out to adjust for potential confounders. For toxicity analysis, the association between the incidence of post-treatment severe GU/GI toxicity reaction, denoted grade 3 or higher, and the treatment group was evaluated via chi-squared or Fisher's exact test. Statistical comparisons for HDR, HDR+EBRT-ADT, and HDR+EBRT+ADT are summarized in Table 1. From the Kaplan-Meier curves and log-rank tests, no differences between the three cohorts were identified in all five survival outcomes (FFBC, FFDM, FFLF, OS, CSS), with 5-year survival for HDR, HDR+EBRT-ADT, and HDR+EBRT+ADT FFBC 99%, 95%, and 94% respectively. Multivariate analysis with Cox PH regression showed no differences in FFBC, FFDM, OS, and CSS with addition of EBT alone, or addition of EBT with ADT. Fine and Gray competing regression showed no difference in outcome for HDR, HDR+EBRT-ADT, and HDR+EBRT+ADT with respect to FFBC, FFDM, and CSS. Performing the likelihood ratio test to both the Cox PH and Fine & Gray competing regression models resulted in no differences in all survival outcomes with stable fits between treatment and non-treatment groups. In comparing CTCAE toxicities between the HDR, HDR+EBRT-ADT, and HDR+EBRT+ADT cohorts, no statistically significant differences were identified in GI and GU toxicities when comparing post-treatment and baseline toxicities. No Grade 2 or 3 GI toxicities were identified in any of the groups, while 8% and 1% of HDR patients, 10% and 1% of HDR+EBRT-ADT patients, and 12% and 2% of HDR+EBRT+ADT patients experienced Grade 2 or 3 GU toxicities. The presence of grade 3 or higher GU toxicities between the three groups were not found to be significant (p=0.91). The results of this study demonstrate the non-inferiority of HDR BT treatment alone for UIR prostate cancer when compared to HDR+EBRT +/- ADT. The omission of EBRT, with or without ADT, can theoretically minimize occurrence of associated toxicities, although the data in this study do not demonstrate statistically significant differences likely due to the overall low frequency of toxicities reported. Given patients' often reluctance in undergoing multiple procedures, especially when faced with the side effect profile of ADT, these results illuminate a viable road for HDR BT monotherapy in effective and durable control of UIR disease. [ABSTRACT FROM AUTHOR]

Purpose There is a lack of prescriptive, practical information for those doing the work of commissioning high-dose-rate (HDR) gynecologic (GYN) treatment equipment. The purpose of this work is to develop a vendor-neutral, consensus-based, commissioning template to improve standardization of the commissioning process. Methods and Materials A series of commissioning procedures and tests specific to HDR GYN treatments were compiled within one institution. The list of procedures and tests was then sent to five external reviewers at clinics engaged in HDR GYN treatments. External reviewers were asked to ( 1 ) suggest deletions, additions, and improvements/modifications to descriptions, ( 2 ) link the procedures and tests to common, severe failure modes based on their effectiveness at mitigating those failure modes, and ( 3 ) rank the procedures and tests based on perceived level of importance. Results External reviewers suggested the addition of 14 procedures and tests. The final template consists of 67 procedures and tests. “Treatment process” and “staff training” sections were identified as mitigating the highest number of commonly reported failure modes. The mean perceived importance for all procedures and tests was 4.4 of 5, and the mean for each section ranged from 3.6 to 4.8. Sections of the template that were identified as mitigating the highest number of commonly reported failure modes were not assigned the highest perceived importance. Conclusion The commissioning template developed here provides a standardized approach to process and equipment commissioning. The discord between perceived importance and mitigation of the highest number of failure modes suggests that increased focus should be placed on procedures and tests in “treatment process” and “staff training” sections. [ABSTRACT FROM AUTHOR]

Purpose: High-dose-rate (HDR) brachytherapy was originally used with external beam radiation therapy (EBRT) to increase the dose to the prostate without injuring the bladder or rectum. Numerous studies have reported HDR brachytherapy is safe and effective. We adapted it for use without EBRT for cases not requiring lymph node treatment.Patients and Methods: We entered the patient demographics, disease characteristics, and treatment parameters into a prospective registry and serially added follow-up data for 448 men with low-risk (n=288) and intermediate-risk (n=160) prostate cancer treated from 1996 to 2009. Their median age was 64 years (range 42-90). The median prostate-specific antigen (PSA) level was 6.0 ng/mL (range 0.2-18.2). The Gleason score was ≤6 in 76% and 7 in 24%. The median dose was 43.5 Gy in 6 fractions. The clinical and biochemical disease control and survival rates were calculated. Adverse events were graded according to the Common Toxicity Criteria of Adverse Events.Results: The median follow-up period was 6.5 years (range 0.3-15.3). The actuarial 6- and 10-year PSA progression-free survival was 98.6% (95% confidence interval [CI] 96.9%-99.4%) and 97.8% (95% CI 95.5%-98.9%). Overall survival at 10 years was 76.7% (95% CI 69.9%-82.2%). The local control, distant metastasis-free survival, and cause-specific survival were 99.7% (95% CI 97.9%-99.9%), 98.9% (95% CI 96.3%-99.7%), and 99.1% (95% CI 95.8%-99.8%). T stage, initial PSA level, Gleason score, National Comprehensive Cancer Network risk group, patient age, and androgen deprivation therapy did not significantly correlate with disease control or survival. No late grade 3 to 4 rectal toxicities developed. Late grade 3 to 4 genitourinary toxicity occurred in 4.9% (grade 3 in 4.7%).Conclusions: HDR monotherapy is a safe and highly effective treatment of low- and intermediate-risk prostate cancer. [ABSTRACT FROM AUTHOR]

Purpose To determine the utility of ureteral stents in interstitial gynecological brachytherapy. Methods and Materials We reviewed 289 patients with cervix cancer treated with high-dose-rate interstitial brachytherapy who did not have pretreatment hydronephrosis to determine the relative incidence of benign ureteral strictures after treatment. We also did comparative dosimetry analysis in five cases of high-dose-rate brachytherapy. Bilateral ureteral stents were placed during the procedure. Three dosimetry plans were created to determine the impact of modifying clinical target volume (CTV) and applying ureteral dose constraints. In Plan 1, the ureters were contoured and excluded from the CTV and 120% dose constraints were applied. In Plan 2, the ureters were contoured and excluded, but no dose constraints were applied to the ureter. In Plan 3, the CTV was created as if the location of the ureters was unknown and then ureteral dose was determined. Results There were 11 ureteral strictures observed in 255 nonstented cases and 0 ureteral strictures in 34 stented cases. Plan 1 reduced the ureter dose (D 0.1cc ) by a median 22% (7.0–53.8%) compared with Plan 2 and by a median of 30.9% (12.3–65%). compared with Plan 3. Conclusions Placement of stents and ureteral dose constraints facilitates dosimetry and reduces the dose to ureters. Temporary ureteral stents prevent obstruction during interstitial gynecologic brachytherapy and allows the ureters to be addressed as an organ at risk. [ABSTRACT FROM AUTHOR]