High Dose Rate Brachytherapy Research Articles

Clinical Outcomes of Sidewall/Parametrial Simultaneous Integrated Boost for Patients with Cervical Cancer

In the treatment of cervical cancer, simultaneous integrated boost (SIB) is a common technique to deliver increased dose to gross disease in the para-aortic and pelvic nodal basins. However, SIB to the pelvic sidewall/parametria is not well characterized in the literature. We hypothesized that sidewall simultaneous integrated boost (SIB) in the treatment of cervical cancer is associated with acceptable levels of toxicity. From 1/2009-12/2018, patients who received concurrent chemoradiation with external beam radiation therapy, utilizing a sidewall SIB technique, followed by low dose rate or high dose rate brachytherapy treatment were retrospectively identified. Sidewall SIB was defined as treatment at 2.1-2.4Gy/fraction to the parametria-usually performed for those with disease width >4cm at time of treatment start. Acute and late toxicity grading was defined by the Common Terminology Criteria for Adverse Events Version 5.0. Overall survival (OS), local control, progression-free survival (PFS), and toxicity were analyzed utilizing the Kaplan Meier method. Potential associations between cumulative D2cc for bladder and rectum and time to toxicity were investigated using Cox regression. Fifty-six patients with IB2-IVB cervical cancer treated with sidewall SIB were identified, with a median follow up of 7.0 years (95% CI: 6.3, 8.3). Patients had a median age of 43 years (range: 26-68); 2 (3.6%) had FIGO stage I, 7 (12.5%) stage II, 46 (82.1%) stage III, and 1 (1.8%) stage IV disease. A majority had squamous cell histology (83.9%). Nearly all patients (96.4%) received concurrent cisplatin chemotherapy. Rates of acute grade ≥3 gastrointestinal (GI), genitourinary (GU), vaginal, and hematologic toxicity were 1.8%, 1.8%, 0%, and 15.9% respectively. Rates of late grade ≥3 GI, GU, and vaginal toxicity were 11.3%, 18.5%, and 11.1% respectively. OS and local control rates at five years were 0.61 (95% CI: 0.46, 0.73) and 0.95 (95% CI: 0.84, 0.98), respectively. Median PFS was 7.8 years (95% CI: 2.4, Not reached). Cumulative D2cc bladder was not significantly associated with time to Grade 2 or greater (HR 1.04, p = 0.33) or Grade 3 or greater (HR 1.02; p = 0.64) GU toxicity. Cumulative D2cc rectum was not significantly associated with time to Grade 2 or greater (HR 1.06, p = 0.06) or Grade 3 or greater (HR 1.08; p = 0.09) GI toxicity. Sidewall SIB is a feasible technique for dose escalation in the treatment of cervical cancer with rates of acute and late toxicity consistent with other reports.

Phase III Study of Hypofractionated, Dose Escalation Radiotherapy vs. Conventional Pelvic Radiation Therapy followed by High Dose Rate Brachytherapy Boost for High Risk Adenocarcinoma of the Prostate (PCS VI): Acute Toxicity Results

The low α\β ratio of 1.2-2 for prostate cancer (PCa) suggests high radiation-fraction sensitivity and predicts a therapeutic advantage of lager fraction size. We have recently shown (PCS5) that high risk prostate cancer patients can safely and effectively be treated with moderate hypofractionated radiation therapy (HF-RT). To date there has been no phase-III randomized clinical-trial comparing moderately HF-RT with EBRT and HDR boost (HDRB). We are reporting the acute safety of EBRT+HDRB compared to moderate HF-RT in this phase III Canadian trial. From January 2015-June 2022, 308 high-risk localized PCa patients were randomized to receive either HF-RT or EBRT+HDRB. All patients received neo-adjuvant, concurrent, and long-term adjuvant androgen deprivation therapy (ADT). EBRT+HDRB consisted of 46 Gy in 2 Gy per fraction to the pelvis and a 15 Gy in one fraction HDR boost within 3 weeks of EBRT. HF-RT include concomitant dose escalation of 68 Gy in 2.72 Gy per fraction to the prostate, and 45 Gy in 1.8 Gy per fraction to the pelvic lymph-nodes. Of the 308 patients, 148 received HF-RT and 144 EBRT+ HDRB. The remainder either withdrew from the study or were treated with standard (2 Gy per fraction) fractionation for technical reasons. In both intention to treat and as treated analysis, using log-Rank, there were more grade 1 or worse (G1+) acute GI and GU events and more G2+ acute GI events in the HF-RT than EBRT+HDRB. As treated analysis the acute G1+ and G2+ GI events were 92 vs 77 (60.1% vs. 53.5%; p < 0.017) and 21 vs 10 (13.7% vs. 6.9%; p = 0.052), respectively for HF-RT and EBRT + HDRB. Similarly, the G1+ acute GU events were 123 vs. 101 (80.4% vs.70.1%; p < 0.001) respectively for HF-RT and EBRT+HDRB. There were only four G3 GI and one G3 GU acute toxicities in both arms. No grade 4 toxicities were reported. This is the first study of EBRT+HDRB compared to moderate HF dose escalated RT in high-risk prostate cancer patients treated with long-term ADT and pelvic RT. Our results demonstrate that both treatment approaches are well-tolerated and that EBRT+HDRB carries less G2+ GI and G1+ GU acute toxicities.

Communicating the External Beam Radiotherapy Experience (CEBRE) Discussion Guides: Real World Implementation and Evaluation

Communicating about the radiotherapy treatment process can be difficult for patients and healthcare professionals. The "Communicating the External Beam Radiotherapy Experience" (CEBRE) and Communicating the Gynecologic Brachytherapy Experience (CoGBE) discussion guides use graphic narrative to explain external beam radiotherapy and gynecologic high-dose rate brachytherapy, respectively. The CEBRE, CoGBE, and CEBRE en Español guides have been available for free download since 10/2018, 6/2020, and 8/2021, respectively. This study aims to characterize how the guides are being implemented and used in practice. Global downloads of the CEBRE, CoGBE, and CEBRE en Español guides were analyzed. Email addresses submitted at the time of download were used to contact study subjects. Duplicate emails, fake addresses, and expired emails were removed resulting in 500 individuals being invited to participate in the survey. A data collection web application survey was distributed on 1/27/23. Two reminders were sent prior to the survey closing on 2/13/23. The survey addressed how physicians or other radiotherapy team members use the CEBRE guides, where they are used, and how the guides can be improved. Likert-type data (1 = strongly disagree, 5 = strongly agree) are reported as median [interquartile range]. As of 10/16/22, the CEBRE guides (English) had been downloaded 602 times, CoGBE 86 times, and CEBRE en Español 63 times. 42/500 individuals responded to the survey for an 8% response rate. 40/42 (95%) of participants were healthcare providers with 35/40 (87.5%) radiation oncologists. 16/40 (40%) have used the CEBRE guides in some way. 6/16 (37.5%) "always use," 2/16 (12.5%) "often use," and 3/16 (18.8%) "sometimes use" the guides during consultation. 8/16 (50%) report using the guides for education of medical students, residents, and fellows. The 16 respondents that use the guides felt the guides were useful overall (5[5-5]), felt "very confident" using the guides (4.5[4-5]), and felt the guides "help patients prepare for their treatment" (5[4-5]). 40 respondents provided suggestions on additional language translations with 19/40 (48%) recommending translation into Mandarin, 6/40 (15%) into Cantonese, Portuguese, French and Arabic, and 5/40 (12.5%) into Haitian, Hindi, and Vietnamese. The majority of respondents did not use the CEBRE guides which may be due to difficulty with implementation. However, respondents who use the guides are confident using them and rate them as useful for patients. These data, although limited by the low response rate, suggest that the CEBRE guides have accomplished the goal of facilitating patient-physician conversations. Moreover, there is an interest in translating the guides into additional languages other than Spanish. Due to the low response rate, definitive conclusions cannot be made from these data. Therefore, further research such as interviews and focus groups may be beneficial.

A Novel Method for Intracavitary Cervical HDR Brachytherapy: Express Finger-Guided Implant Insertion at Simulation Table without Speculum, Cervical Dilatation, Sleeve, Anesthesia, or Sedation

Our purpose is to develop a fast, effective, and independent intracavitary brachytherapy implant insertion method that does not need sleeve insertion, anesthesia or conscious sedation, and that can be performed at the front edge of the simulation table (CT or MRI), using finger guidance without a need for speculum or cervical dilatation. From February 2022 to January 2023, we treated 27 locally advanced cervical cancer patients. In the last week of EBRT, we assessed patients with MRI and pelvic exam to determine their eligibility: 89% (24 patients) met the two inclusion criteria for the express insertion which are: the ability to cover any residual disease with intracavitary brachytherapy, and the accessibility of cervix external os. Each patient had 3 HDR express insertions (8Gy x3). A total of 72 consecutive express implant insertions were performed. Each insertion is evaluated for the success of procedure, number of attempts, and time taken. Patients started on laxative 3 days prior to the procedure, and paracetamol & Ibuprofen taken at home 2 hours before the procedure. On arrival, patients used the bathroom, and IM/SC morphine given. Patients were prepared at the front edge of the simulation table and topical lidocaine applied to the cervix. The external os identified with the index finger of one hand which also guided the tandem insertion using the other hand. No cervical dilatation was used. CT simulation was performed to confirm adequate implant placement and to contour and plan CTV-HR and OARs as per GEC-ESTRO/ABS guidelines. The success rate was 100% in all the 72 express insertions. >90% (66 insertions) were smooth and fast, i.e., completed in 1 attempt that took <20 minutes. <10% (6 insertions) were challenging but successful, in 2 patients: one patient had an acute anteverted uterus for which suprapubic abdominal pressure facilitated the procedure that took <3 attempts and completed in <40 minutes, the other patient had an acute retroverted uterus which was associated with the most challenging procedure that took >3 attempts and completed in >40 minutes. The success rate was not affected by the type of applicator used. 85% of our applications used multichannel tandem and cylinder, 10% used tandem and ovoids, and 5% used tandem and ring applicators. Express finger-guided intracavitary brachytherapy implant insertion at the simulation table without speculum, cervical dilatation, sleeve, anesthesia, or sedation is fast, effective, and an independent method that can be used in most cervical cancer patients to complete their planned brachytherapy treatment regardless of limited resources. Practice and dissemination of this innovative method is important especially when operative rooms and anesthesia support are limited (e.g., epidemics and closures) and in centers lacking such support. Further studies are warranted to optimize the procedure and to highlight its significant medical and socioeconomic benefits.

A 3D Deep Convolutional Neural Network for Dose Distribution Prediction of Intracavitary HDR Brachytherapy of Cervical Cancer

The purpose of this work is to develop a voxel-wise dose prediction model using convolutional neural network (CNN) for cervical cancer high-dose-rate (HDR) intracavitary brachytherapy treatment planning with tandem-and-ovoid (T&O) or tandem-and-ring (T&R) applicators. A 3D U-NET CNN was implemented to generate voxel-wise dose predictions based on high-risk clinical target volume (HRCTV) and organs at risk (OAR) contour information. A multi-institutional cohort of 77 retrospective clinical HDR brachytherapy plans treated to a prescription dose in the range of 4.8-7.0 Gy/fx was used in this study. Those plans were randomly divided into 60%/20%/20% as training, validating, and testing cohorts. Data augmentation techniques were implemented in the training and validation cohort data to increase the number of plans to 252. The model was trained using the mean-squared loss function, Adam optimization algorithm, a learning rate of 0.001, 250 epochs, and a batch size of 8. The model performance was evaluated on the testing dataset by analyzing the outcomes in terms of mean dose values and derived dose-volume-histogram (DVH) indices from 3D dose distributions and comparing the generated dose distributions against the ground-truth dose distributions using dose statistics and clinically meaningful dosimetric indices. The proposed 3D U-Net model showed competitive accuracy in predicting 3D dose distributions that closely resemble the ground truth dose distributions. The average value of mean absolute error was 0.108±3.617 Gy for HRCTV, 0.074±1.315 Gy for bladder, 0.093±0.981 Gy for rectum, and 0.035±2.789 Gy for sigmoid. The median absolute error was 1.264 Gy for HRCTV, 0. 441 Gy for the bladder, 0.018 Gy for rectum, and 0.019 Gy for sigmoid. Our results showed that the predicted mean D2cc OAR doses in the bladder, rectum, and sigmoid were 4.02±0.93, 3.77±0.57 and 3.36±0.82 Gy in comparison to 4.35±0.98, 3.99±0.53, 3.75±0.83 Gy in clinical plans, respectively, and the mean individual differences (ΔD2cc) were 0.33±0.41, 0.22±0.16 and 0.39±0.45 Gy, respectively. The predicted D90 of the HRCTV was 6.72±0.99 Gy in comparison with 6.83±1.72 Gy in clinical plans. Results indicate a good potential to predict useful dosimetric indices and thus would facilitate an improvement in brachytherapy treatment planning workflow. The proposed model needs less than 5 seconds to predict a full 3D dose distribution of 64 × 64 × 64 voxels for any new patient plan, thus making it sufficient for near real-time applications and aid in decision-making in clinic. The proposed model can be used to predict 3D dose distributions for near real-time decision-making, before planning, for planning quality assurance, and for guiding future automated planning for improved plan consistency, quality, and planning efficiency.

Combining Novel Direction Modulated Brachytherapy Tandem-and-Ovoids Applicators for Treatment Planning of Multi-Institutional Cervical Cancer Cases: Removing Needles in Intracavitary-Interstitial Techniques

Lack of standard guidelines for optimal needle insertion during high-dose-rate (HDR) intracavitary-interstitial (IC-IS) brachytherapy of the cervix means a sophisticated and technical skillset of inserting needles next to IC applicators must be developed to enhance plan quality. This study sought to evaluate the performance of two separate direction modulated brachytherapy (DMBT) tandem applicators used in conjunction with one set of novel DMBT ovoids, uniquely designed to effectively obviate the need for IS needles. A cohort of 32 retrospective clinical HDR brachytherapy plans, from three institutions, were re-planned with Varian's BrachyVision® (v16.1) treatment planning system (BV-TPS), using the latest VEGO® inverse optimization algorithm, with dose heterogeneity accounted for through the AcurosBV®. All plans consisted of IC-IS cases, with a range of 2-4 freehand-loaded needles, with an average prescription dose of 709±53 cGy, and with an average high-risk clinical target volume (HRCTV) of 36.73±17.15 [range 9.8-69.6] cm3. Two DMBT tandem models of 5.4-mm and 8.0-mm thicknesses along with a novel DMBT ovoids design, introduced for the first time, with 9 equi-angled grooves and 10-mm-diameter thickness. During re-planning, the conventional tandems, ovoids/rings, and all of the needles were replaced by one of the two DMBT tandem models and a set of DMBT ovoids. A two-step inverse optimization process was performed to achieve the lowest possible OAR D2cc doses while 1) keeping equivalent target coverage (ΔHRCTV-D90 to within ±0.5%) and 2) maintaining the general pear-shape dose distribution used by the original plans. For all plans, this process was repeated using each of the two DMBT tandem-and-ovoids combinations for a total re-planning of (32×2 =) 64 cases. On average, -47.15±29.61 (-40.40±34.90) cGy, -42.98±26.58 (-41.70±27.40) cGy, and -40.47±25.05 (-32.55±25.30) cGy reductions in D2cc across bladder, rectum, and sigmoid, respectively, were achieved for the 8-mm (5.4-mm) DMBT tandem-and-ovoids combinations while the average ΔHRCTV-D90 was +4.3±2.9 cGy (+0.5%±0.4%). Additionally, D2cc reductions in terms of EQD2 [Gy] were calculated and showed significant reductions of -4.05±2.47 (-3.37±2.83) Gy, -2.71±1.79 (-2.59±1.74) Gy, and -3.27±1.96 (-2.65±2.06) Gy for bladder, rectum, and sigmoid, respectively with an average net increase in total dwell times of 241.0±87.6 seconds at the luxury of avoiding IS needle insertions. It is clinically feasible to obviate the need for IS needles by incorporating the DMBT tandem-and-ovoids while producing lower OAR D2cc doses and maintaining equivalent target coverage.

High-Dose Rate Brachytherapy Combined with PD-1 Blockade as a Treatment for Metastatic Adrenocortical Carcinoma - A Single Center Case Series.

The response rate of advanced adrenocortical carcinoma (ACC) to standard chemotherapy with mitotane and etoposide/doxorubicin/cisplatin (EDP-M) is unsatisfactory, and benefit is frequently short lived. Immune checkpoint inhibitors (CPI) have been examined in patient's refractory to EDP-M, but objective response rates are only approximately 15%. High-dose rate brachytherapy (HDR-BT) is a catheter-based internal radiotherapy and expected to favorably combine with immunotherapies. Here we describe three cases of patients with advanced ACC who were treated with HDR-BT and the CPI pembrolizumab. None of the tumors were positive for established response markers to CPI. All patients were female, had progressed on EDP-M and received external beam radiation therapy for metastatic ACC. Pembrolizumab was initiated 7 or 23 months after brachytherapy in two cases and prior to brachytherapy in one case. Best response of lesions treated with brachytherapy was complete (n=2) or partial response (n=1) that was ongoing at last follow up after 23, 45 and 4 months, respectively. Considering all sites of tumor, response was complete and partial remission in the two patients with brachytherapy prior to pembrolizumab. The third patient developed progressive disease with severe Cushing's syndrome and died due to COVID-19. Immune-related adverse events of colitis (grade 3), gastroduodenitis (grade 3), pneumonitis (grade 2) and thyroiditis (grade 1) occurred in the two patients with systemic response. HDR-BT controlled metastases locally. Sequential combination with CPI therapy may enhance an abscopal antitumoral effect in non-irradiated metastases in ACC. Systematic studies are required to confirm this preliminary experience and to understand underlying mechanisms.

Высокомощностная брахитерапия в монорежиме у пациентов с локализованным раком предстательной железы.

Introduction. Prostate cancer is the second most common cancer among men. In Russia the number of patients with stage I-II prostate cancer increased from 47,7% in 2010 to 60,7% in 2021. One of the main methods of treatment of localized prostate cancer is high-dose-rate brachytherapy, which today provides high accuracy of prostate dose coverage and minimizes the impact on nearby risk organs. Within ever-increasing publications, high-dose-rate brachytherapy is considered as a method of safe and effective radical treatment of prostate cancer. Materials and methods. Relevant publications were searched for in the PubMed and е-Library databases with the use of the keywords «brachytherapy», «highdose-rate brachytherapy», «brachytherapy as monotherapy». As a result of the search, 52 sources were selected and included in the given literature review. Results and discussion. The first report on the use of brachytherapy as monotherapy appeared in 2000 where published the results of treatment and demonstrated the safety and effectiveness of the method. Despite the large number of studies conducted all over the world with various options of dose delivery per fraction, the optimal dose and fractionation mode for high-dose-rate brachytherapy as monotherapy have not been determined yet. Conclusions. Currently high-dose-rate brachytherapy of localized prostate cancer as monotherapy has become widespread. However, the available modern data on fractionation modes require further study and research.

Six-probe scintillator dosimeter for treatment verification in HDR-brachytherapy.

In vivo dosimetry (IVD) is gaining interest for treatment delivery verification in HDR-brachytherapy. Time resolved methods, including source tracking, have the ability both to detect treatment errors in real time and to minimize experimental uncertainties. Multiprobe IVD architectures holds promise for simultaneous dose determinations at the targeted tumor and surrounding healthy tissues while enhancing measurement accuracy. However, most of the multiprobe dosimeters developed so far either suffer from compactness issues or rely on complex data post-treatment. We introduce a novel concept of a compact multiprobe scintillator detector and demonstrate its applicability in HDR-brachytherapy. Our fabricated seven-fiber probing system is sufficiently narrow to be inserted in a brachytherapy needle or in acatheter. Our multiprobe detection system results from the parallel implementation of six miniaturized inorganic Gd2 O2 S:Tb scintillator detectors at the end of a bundle of seven fibers, one fiber is kept bare to assess the stem effect. The resulting system, which is narrower than 320 microns, is tested with a MicroSelectron 9.14 Ci Ir-192 HDR afterloader, in a water phantom. The detection signals from all six probes are simultaneously read with a sCMOS camera (at a rate of 0.06 s). The camera is coupled to a chromatic filter to cancel Cerenkov signal induced within the fibers upon exposure. By implementing an aperiodic array of six scintillating cells along the bundle axis, we first determine the range of inter-probe spacings leading to optimal source tracking accuracy (first tracking method). Then, three different source tracking algorithms involving all the scintillating probes are tested and compared. In each of these four methods, dwell positions are assessed from dose measurements and compared to the treatment plan. Dwell time is also determined and compared to the treatmentplan. The optimum inter-probe spacing for an accurate source tracking ranges from 15 to 35 mm. The optimum detection algorithm consists of adding the readout signals from all detector probes. In that case, the error to the planned dwell positions is of 0.01 ± 0.14 mm and 0.02 ± 0.29 mm at spacings between the source and detector axes of 5.5 and 40 mm, respectively. Using this approach, the average deviations to the expected dwell time are of s and s, at spacings between source and probe axes of 5.5 and 20 mm,respectively. Our six-probe Gd2 O2 S:Tb dosimeter coupled to a sCMOS camera can perform time-resolved treatment verification in HDR brachytherapy. This detection system of high spatial and temporal resolutions (0.25 mm and 0.06 s, respectively) provides a precise information on the treatment delivery via a dwell time and position verification of unmatched accuracy.

A scintillation dosimeter with real-time positional tracking information for in vivo dosimetry error detection in HDR brachytherapy.

To evaluate the performance of an electromagnetic (EM)-tracked scintillation dosimeter in detecting source positional errors of IVD in HDR brachytherapy treatment. Two different scintillator dosimeter prototypes were coupled to 5 degrees-of-freedom (DOF) EM sensors read by an Aurora V3 system. The scintillators used were a 0.3 × 0.4 × 0.4 mm3 ZnSe:O and a BCF-60 plastic scintillator of 0.5 mm diameter and 2.0 mm in length (Saint-Gobain Crystals). The sensors were placed at the dosimeter's tip at 20.0 mm from the scintillator. The EM sampling rate was 40/s while the scintillator signal was sampled at 100 000/s using two photomultiplier tubes from Hamamatsu (series H10722) connected to a data acquisition board. A high-pass filter and a low-pass filter were used to separate the light signal into two different channels. All measurements were performed with an afterloader unit (Flexitron-Elekta AB, Sweden) in full-scattered (TG43) conditions. EM tracking was further used to provide distance/angle-dependent energy correction for the ZnSe:O inorganic scintillator. For the error detection part, lateral shifts of 0.5 to 3 mm were induced by moving the source away from its planned position. Indexer length (longitudinal) errors between 0.5 to 10 mm were also introduced. The measured dose rate difference was converted to a shift distance, with and without using the positional information from the EMsensor. The inorganic scintillator had both a signal-to-noise-ratio (SNR) and signal-to-background-ratio (SBR) close to 70 times higher than those of the plastic scintillator. The mean absolute difference from the dose measurement to the dose calculated with TG-43U1 was 1.5% ±0.7%. The mean absolute error for BCF-60 detector was 1.7% when compared to TG-43 calculations formalism. With the inorganic scintillator and EM tracking, a maximum area under the curve (AUC) gain of 24.0% was obtained for a 0.5-mm lateral shift when using the EMT data with the ZnSe:O. Lower AUC gains were obtained for a 3-mm lateral shifts with both scintillators. For the plastic scintillator, the highest gain from using EM tracking information occurred for a 0.5-mm lateral shift at 20 mm from the source. The maximal gain (17.4%) for longitudinal errors was found at the smallest shifts (0.5 mm). This work demonstrates that integrating EM tracking to in vivo scintillation dosimeters enables the detection of smaller shifts, by decreasing the dosimeter positioning uncertainty. It also serves to perform position-dependent energy correction for the inorganic scintillator,providing better SNR and SBR, allowing detection of errors at greater distances from thesource.

The American Brachytherapy Society and Indian Brachytherapy Society consensus statement for the establishment of high-dose-rate brachytherapy programs for gynecological malignancies in low- and middle-income countries

PURPOSEThe global cervical cancer burden is disproportionately high in low- and middle-income countries (LMICs), and outcomes can be governed by the accessibility of appropriate screening and treatment. High-dose-rate (HDR) brachytherapy plays a central role in cervical cancer treatment, improving local control and overall survival. The American Brachytherapy Society (ABS) and Indian Brachytherapy Society (IBS) collaborated to provide this succinct consensus statement guiding the establishment of brachytherapy programs for gynecological malignancies in resource-limited settings. METHODS AND MATERIALSABS and IBS members with expertise in brachytherapy formulated this consensus statement based on their collective clinical experience in LMICs with varying levels of resources. RESULTSThe ABS and IBS strongly encourage the establishment of HDR brachytherapy programs for the treatment of gynecological malignancies. With the consideration of resource variability in LMICs, we present 15 minimum component requirements for the establishment of such programs. Guidance on these components, including discussion of what is considered to be essential and what is considered to be optimal, is provided. CONCLUSIONSThis ABS/IBS consensus statement can guide the successful and safe establishment of HDR brachytherapy programs for gynecological malignancies in LMICs with varying levels of resources.

Observer preference of artificial intelligence-generated versus clinical prostate contours for ultrasound-based high dose rate brachytherapy.

For trans-rectal ultrasound (TRUS)-based high dose rate (HDR) prostate brachytherapy, prostate contouring can be challenging due to artifacts from implanted needles, bleeding, and calcifications. To evaluate the geometric accuracy and observer preference of an artificial intelligence (AI) algorithm for generating prostate contours on TRUS images with implanted needles. We conducted a retrospective study of 150 patients, who underwent HDR brachytherapy. These patients were randomly divided into training (104), validation (26) and testing (20) sets. An AI algorithm was trained/validated utilizing the TRUS image and reference (clinical) contours. The algorithm then provided contours for the test set. For evaluation, we calculated the Dice coefficient between AI and reference prostate contours. We then presented AI and reference contours to eight clinician observers, and asked observers to select their preference. Observers were blinded to the source of contours. We calculated the percentage of cases in which observers preferred AI contours. Lastly, we evaluate whether the presence of AI contours improved the geometric accuracy of prostate contours provided by five resident observers for a 10-patient subset. The median Dice coefficient between AI and reference contours was 0.92 (IQR: 0.90-0.94). Observers preferred AI contours for a median of 57.5% (IQR: 47.5, 65.0) of the test cases. For resident observers, the presence of AI contours was associated with a 0.107 (95% CI: 0.086, 0.128; p<0.001) improvement in Dice coefficient for the 10-patient subset. The AI algorithm provided high-quality prostate contours on TRUS with implanted needles. Further prospective study is needed to better understand how to incorporate AI prostate contours into the TRUS-based HDR brachytherapy workflow.

46 Patterns of Relapse and Biochemical Control in Intermediate Risk Prostate Cancer Treated with High Dose Rate Brachytherapy (HDRB) Monotherapy

46 Patterns of Relapse and Biochemical Control in Intermediate Risk Prostate Cancer Treated with High Dose Rate Brachytherapy (HDRB) Monotherapy

MSOR04 Presentation Time: 8:45 AM: Outcomes with High Dose Rate Brachytherapy in Reirradiation of Head and Neck Cancers

MSOR04 Presentation Time: 8:45 AM: Outcomes with High Dose Rate Brachytherapy in Reirradiation of Head and Neck Cancers

166 Deep Learning-Based Transfer of TG-43 Based Dose to Water to Dose to Medium in Medium in High Dose Rate Brachytherapy

166 Deep Learning-Based Transfer of TG-43 Based Dose to Water to Dose to Medium in Medium in High Dose Rate Brachytherapy

PO07: Definitive Radiotherapy of Vulvar and Vaginal Melanoma with High Dose Rate Brachytherapy and Hyperthermia

PO07: Definitive Radiotherapy of Vulvar and Vaginal Melanoma with High Dose Rate Brachytherapy and Hyperthermia

44 Dosimetric Parameters Predictive of Treatment-Related Toxicity in High Dose-Rate Brachytherapy as Monotherapy for Prostate Cancer

44 Dosimetric Parameters Predictive of Treatment-Related Toxicity in High Dose-Rate Brachytherapy as Monotherapy for Prostate Cancer

PO125: Feasibility of a Tungsten-181 Source for Use in High Dose-Rate Brachytherapy

PO125: Feasibility of a Tungsten-181 Source for Use in High Dose-Rate Brachytherapy

PO59: Dosimetric Parameters Predictive of Treatment-Related Toxicity in High Dose-Rate Brachytherapy as Monotherapy for Prostate Cancer

PO59: Dosimetric Parameters Predictive of Treatment-Related Toxicity in High Dose-Rate Brachytherapy as Monotherapy for Prostate Cancer

PO73: DIL-Concentrated PSA as a Predictor of Local Recurrence after HDR Brachytherapy in Primary Prostate Cancer

PO73: DIL-Concentrated PSA as a Predictor of Local Recurrence after HDR Brachytherapy in Primary Prostate Cancer