Brachytherapy Treatment Research Articles

Tumor control after palliative hypofractionated, "Quad-shot," external beam radiotherapy followed by brachytherapy: An effective approach in medically compromised and/or elderly patients with cervix cancer.

Cervix cancer is still a leading cause of death in developing countries. Concurrent chemoradiation (CCRT) over 5 weeks followed by brachytherapy is standard of care in locoregionally advanced cervix cancer. Such prolonged treatment may not be tolerated in medically compromised patients. High-dose interrupted hypofractionated Quad-Shot (QS) radiotherapy with brachytherapy treatment was well tolerated. This study aims to assess the locoregional tumor control in cervix cancer patients who were treated with QS regimen. Retrospective. Newly diagnosed histologically confirmed cervix cancer patients who were unfit for conventional CCRT and who were treated with QS protocol between 1999 and 2016 were analyzed. Tumor stage, treatment, and follow-up details were retrieved from an ethics-approved prospective departmental database. Descriptive statistics and Kaplan-Meier method were used for estimating survival. Thirty-six patients were available for analysis. The median age was 70.5 (32-92) years. Twenty-two of 36 (61.1%) patients had nodal disease while 33% of all patients had distant metastasis. Of 27 patients who died during follow-up, the local and pelvic control was 75% and 60%, respectively. The median overall survival and progression-free survival were 18.6 months. Grade 3-4 toxicity was observed (16%) in the bowel only. Hypofractionated QS radiotherapy with brachytherapy resulted in an overall 82.1% at least stable disease at the primary site. This treatment regimen was well tolerated and may be considered appropriate for patients who may not be suitable for conventional fully fractionated CCRT.

The Experience of Pain and Anxiety in Cervical Cancer Patients Undergoing Multiple Fraction High-Dose Rate Brachytherapy: A Prospective Observational Study

Purpose: To evaluate the anxiety and pain levels of cervical cancer patients undergoing intracavitary multifraction high-dose rate (HDR) brachytherapy, as part of a process to develop guidelines for quality patient-centered care. Methods: Cervical cancer patients (n = 31) undergoingmultiple fraction HDR brachytherapy treatment at the National Institute of Oncology in Rabat (Morocco) completed ratings of pain and anxiety intensity using 11-point verbal analog scales, at 6 key time points over 2 brachytherapy insertion procedures and 4 brachytherapy fractions. Women were evaluated for psychological status at baseline before starting the brachytherapy process using the Hospital Anxiety and Depression Scale (HADS). Scores were grouped as follows: 0 - 7 = normal, 8 - 10 = borderline, 11 - 21 = abnormal. Factors that could affect anxiety levels such as education level, relationship status, number of pregnancies and prior surgical history were documented. Results: Between July and August 2020, 31 women with a median age of 49.6 years were evaluated (range: 27 - 70). The HADS score identified depression in 5 patients (16.1%) and anxiety in 12 patients (38.7%). Throughout both treatment procedures, anticipatory anxiety was reported, with a maximum intensity in the operating room during spinal anesthesia (3.23 ± 1.7) and during applicator insertion (2.97 ± 2.4). Moderate-to-severe anxiety scores were reported in 25.8% and 22.6% of patients respectively. Level of education showed a significant correlation with anxiety scores (p = 0.027). Pain increased significantly during the procedure (p ± 1.4) and applicator removal (4.74 ± 1.5) turned out to be the most painful parts of the procedure. No correlation was found between pain and anxiety levels. Conclusion: Intracavitary multifraction high-dose rate brachytherapy is associated with mild to moderate levels of pain and anxiety, although a subset of patients reported more severe symptoms and may require additional medical and psychological support, with particular emphasis on bed-rest duration and applicator removal. The development of effective interventions (both pharmacological and non-pharmacological) is needed to improve women’s experiences of brachytherapy for locally advanced cervical cancer.

Weakly Supervised MR-TRUS Image Synthesis for Brachytherapy of Prostate Cancer.

Prostate magnetic resonance imaging (MRI) offers accurate details of structures and tumors for prostate cancer brachytherapy. However, it is unsuitable for routine treatment since MR images differ significantly from trans-rectal ultrasound (TRUS) images conventionally used for radioactive seed implants in brachytherapy. TRUS imaging is fast, convenient, and widely available in the operation room but is known for its low soft-tissue contrast and tumor visualization capability in the prostate area. Conventionally, practitioners usually rely on prostate segmentation to fuse the two imaging modalities with non-rigid registration. However, prostate delineation is often not available on diagnostic MR images. Besides, the high non-linear intensity relationship between two imaging modalities poses a challenge to non-rigid registration. Hence, we propose a method to generate a TRUS-styled image from a prostate MR image to replace the role of the TRUS image in radiation therapy dose pre-planning. We propose a structural constraint to handle non-linear projections of anatomical structures between MR and TRUS images. We further include an adversarial mechanism to enforce the model to preserve anatomical features in an MR image (such as prostate boundary and dominant intraprostatic lesion (DIL)) while synthesizing the TRUS-styled counterpart image. The proposed method is compared with other state-of-art methods with real TRUS images as the reference. The results demonstrate that the TRUS images synthesized by our method can be used for brachytherapy treatment planning for prostate cancer.

Dosimetric comparison of two afterloaders and treatment planning systems in vaginal high-dose-rate brachytherapy.

PurposeIn treatment planning for high-dose-rate (HDR) single-channel vaginal cylinder brachytherapy, dose distribution along the cylinder is influenced by the anisotropy of the source. Differences in anisotropy are due to differences in source dimensions and characteristics. In this study, we compared HDR vaginal cylinder brachytherapy treatment plans from two afterloader/treatment planning systems.Material and methodsSeventy-five plans with prescription to the surface were generated for cylinders in Varian BrachyVision and Elekta Oncentra. To understand the impact of source anisotropy on dose distribution to the surface of the cylinder, potential effect caused by differences in cylinder geometry between systems was eliminated by re-planning Varian cylinder using Elekta source model. Mean relative dose was calculated for each point as well as the dome and length of the cylinder. Related-samples Wilcoxon signed-rank tests were performed to compare the mean relative dose between systems.ResultsTreatment plans with VariSource iX source and cylinder demonstrated 16.2% lower (p < 0.001) dose at the tip compared to Elekta v.3. Average dose to the points along the dome of cylinder was 128.4% ±17.9% prescription dose with VariSource iX source and cylinder, and 99.9% ±4.3% with Elekta v.3 source and cylinder. For the same cylinder geometry, the effect of source characteristics produced up to 36.8% difference in dose homogeneity. When cylinder types were planned with the same source, there was no significant difference in dose distribution.ConclusionsThis study demonstrates that the effect of source characteristics produced up to 37% difference in dose homogeneity when comparing two afterloader/treatment planning systems, independent of cylinder geometry. This insight on variation in dose surrounding source system is imperative for dosimetry considerations. Depending on the choice of afterloader, the extent of EQD2 for tumor control versus normal tissue toxicity can vary.

The Design of an Audit Test for 60Co Brachytherapy Treatment Planning System.

Background:Auditing the treatment planning system (TPS) software for a radiotherapy unit is of paramount importance in any radiation therapy department. A Plexiglas phantom was proposed to measure the ionization of 60Co high dose rate (HDR) source and compare dose points in the planning system for auditing and verifying TPS.Methods:Auditing was performed using a Plexiglas phantom in an end-to-end test, and relative dose points were detected by a farmer-type ionization chamber and compared with the relative dose of similar points in TPS. The audit results were determined as pass optimal level (<3.3%), pass action level (between 3.3% and 5%), and out of tolerance (>5%).Results:The comparison of the collected data revealed that 80% of the measured values were ≤5% in the pass level, and 20% of the points were out of tolerance (between 5% and 6.99%).Conclusion:This study documented the appropriateness of the dosimetry audit test and this phantom design for the HDR brachytherapy TPS.

Commissioning Validation of a Brachytherapy Treatment Planning System with EGSnrc Monte Carlo Code and EBT3 GAFChromic Film.

Most brachytherapy treatment planning system (TPS) commissioning requires data input based on the American Association of Physicists in Medicine Task Group-43 formalism. The commissioning accuracy is very important for dose calculation. The aim of this study is the implementation of a brachytherapy TPS into a clinical environment and check the TPS calculated dose accuracy. After introducing data of the different catheters (CIS Bio International, Saclay, France), composed of several Cesium-137 Eckert and Ziegler BEBIG CSM-11 radioactive sources; for XiO (CMS, St. Louis) brachytherapy TPS, the TPS dose calculation accuracy was investigated by comparing between the TPS calculated dose distribution (DD) for all the catheters with (1) the measuring DD using EBT3 GAFChromic film and (2) calculating DD by egs_brachy (Electron Gamma Shower, National Research Council of Canada) Monte Carlo simulation. The phantom used for this study consists of six PTW slabs 30 cm × 30 cm × 1 cm of polymethyl methacrylate with a Delouche MEDpro applicator on the top. The TPS DD was calculated on the computed tomography scan of this phantom. PTW VeriSoft version 6.0.1.7 (PTW-Freiburg, Germany) software was used for analyzing scanned films and to perform the comparison based on the gamma index distribution. For each catheter, the gamma index distribution showed agreement >95% of all pixels in both verification methods, with gamma ≤1. We confirm the commissioning accuracy and that the TPS can be used for clinical purposes.

Artificial intelligence can overcome challenges in brachytherapy treatment planning.

Artificial intelligence can overcome challenges in brachytherapy treatment planning.

Dose to pelvic lymph nodes in locally advanced cervical cancer during high-dose-rate brachytherapy with tandem-ring applicators.

PurposeThe present study aimed to assess the correlation between dose to pelvic lymph nodes and to point B with tandem-ring (TR) applicators for intra-cavitary brachytherapy treatment of locally advanced cervical cancer.Material and methodsCervical cancer patients treated at brachytherapy department of Lucien Neuwirth Cancer Center, from 2015 to 2018, were included. Target delineation was performed in compliance with GEC-ESTRO guidelines. Revised American Brachytherapy Society (ABS) point A was determined (ARN (right) and ALN (left)) as well as Manchester point B. Prescription dose was 25-35 Gy in 5 fractions. Pelvic lymph nodes were delineated, then dose to points A and B, and dose-volume histogram (DVH) parameters of delineated lymph nodes were extracted. Significant relationships or correlations between lymph nodes reference points, dosage to points B, and their DVH parameters were investigated.ResultsThe mean dose and mean percentage of the prescription dose to the left and right points B were 4.6 ±0.18 Gy and 82.08 ±0.72%, respectively. Pearson correlation coefficient R = 0.81 (p-value = 0.00) between dose to ARN and ALN points and prescription dose was obtained. Negative correlation between CTVHR volume and difference between French and ABS prescription points was found.ConclusionsDose to point B can be a moderate surrogate for maximum, minimum, and median dose to the internal iliac and presacral lymph node, but cannot be for maximum dose to the obturator lymph node. Points B cannot be a reliable substitute for common and external iliac chains.

Reliability of algebraic sum to evaluate adjuvant pelvic radiotherapy and vaginal cuff brachytherapy cumulative doses in uterine cancers.

To evaluate the reliability of algebraic sum with respect to rigid fusion of treatment plans related to adjuvant external beam pelvic radiotherapy (APR) and vaginal cuff high-dose-rate brachytherapy (BT) in uterine cancer patients. For algebraic sum, APR and BT doses were mathematically added. Rigid fusion was realized overlapping computed tomography (CT) images of APR and BT treatment plans. Rectum and bladder were considered reference organs at risk (OARs). Following dose (D) parameters were examined: Dmax (0.5 cc), D20% and D50% for rectum, Dmax (0.5 cc) and D50% for bladder; for each parameter, differences between the two adopted methods were reported as Δ-values. Twenty uterine cancer patients submitted to radical surgery followed by APR plus vaginal cuff BT were reviewed. APR was done with a dose of 25 × 2 Gy. All patients also receveid a vaginal cuff boost with BT at the dose of 2 × 5 Gy. Differences between mean cumulative doses calculated with rigid fusion and algebraic sum were evaluated. For the rectum and bladder ΔD50%, there were no significant differences, and BT contribution resulted minimal. An apparent significant difference value was registered in bladder ΔDmax (0.5 cc). No toxicity was observed. In uterine cancer patients submitted to APR and vaginal cuff BT, algebraic sum and rigid plan fusion of doses allowed to obtain similar results in evaluating cumulative OARs' doses. Further investigations and increased number of patients are recommended to confirm our findings.

Can we reduce dose to ureters as avoidance organs for MRI based brachytherapy for cervical cancer? A dosimetric feasibility study

BACKGROUND AND PURPOSEUreteral stenosis (US) is an underreported complication of brachytherapy (BT) for cervical cancer (CC), with limited data on toxicity risk reduction. A previous study demonstrated ureter EQD2 D0.1cc > 77 Gy correlated with US development. We sought to assess feasibility of this constraint while maintaining similar HR-CTV coverage. MATERIALS AND METHODSPatients with locally advanced CC treated with EBRT plus HDR MRI-based brachytherapy boost without hydronephrosis at diagnosis and with ureter dose EQD2 D0.1cc > 77 Gy were included. Replan was attempted to achieve HR-CTV D90 ≥ 80–85 Gy and ureter dose reduction. Ureter distance from lateral margin of HR-CTV and tandem was recorded. t-test was performed to compare ureteral dose and HR-CTV D90. RESULTsOf 25 patients were identified. Hundred percent received 45 Gy in 25 fractions to the pelvis ± paraaortic lymph nodes and 80% receiving median additional parametrial dose of 5.4 Gy. Replan meeting ureteral dose of ≤77 Gy was feasible in 18 of 25 patients, with a reduction in median ureter D0.1cc from 82.3 to 76.8 Gy (p < 0.001). Median HR-CTV D90 was similar (84.7 vs. 85.0 Gy). Replan achieved D0.1cc ≤77 Gy in 56% of patients who experienced US. All unilateral US cases occurred in the ureter closest to HR-CTV. CONCLUSIONSOptimization to reduce ureter dose to ≤77 Gy is feasible when ureters are visible and contoured. Ureters may be considered as potential OAR during MRI-based brachytherapy treatment. Reduced ring to tandem total reference air kerma (TRAK) ratio may provide an additional metric by which to lower US risk.

Active small bowel sparing in intracavitary brachytherapy for cervical cancer.

To propose and evaluate an active method for sparing the small bowel in the treatment field of cervical cancer brachytherapy by prone position procedure. The prone position procedure consists of five steps: making bladder empty, prone-positioning a patient on belly board, making the small bowel move to abdomen, filling the bladder with Foley catheter and finally turning the patient into the supine position. The proposed method was applied for the treatment of seven cervical cancer patients. Its effectiveness was evaluated and a correlation between the patient characteristics and the volumetric dose reduction of small bowel was also investigated. Brachytherapy treatment plans were built before and after the proposed method, and their dose-volume histograms were compared for targets and organs-at-risk. In this comparison, all plans were normalized to satisfy the same D90% for high-risk clinical target volume. For the enrolled patients, the average dose of small bowel was significantly reduced from 75.2±4.9Gy before to 60.2±4.0Gy after the prone position procedure, while minor dosimetric changes were observed in rectum, sigmoid and bladder. The linear correlation to body mass index, thickness and width of abdominopelvic cavity and bladder volume were 76.2, 69.7, 28.8 and-36.3%, respectively. The application of prone position procedure could effectively lower the volumetric dose of the small bowel. The dose reduction in the small bowel had a strong correlation with the patient's obesity and abdominal thickness. This means the patients for whom the proposed method would be beneficial can be judiciously selected for safe brachytherapy.

P51 - An end-to-end test for brachytherapy treatment

P51 - An end-to-end test for brachytherapy treatment

Machine-assisted interpolation algorithm for semi-automated segmentation of highly deformable organs.

Accurate and robust auto-segmentation of highly deformable organs (HDOs), for example, stomach or bowel, remains an outstanding problem due to these organs' frequent and large anatomical variations. Yet, time-consuming manual segmentation of these organs presents a particular challenge to time-limited modern radiotherapy techniques such as on-line adaptive radiotherapy and high-dose-rate brachytherapy. We propose a machine-assisted interpolation (MAI) that uses prior information in the form of sparse manual delineations to facilitate rapid, accurate segmentation of the stomach from low field magnetic resonance images (MRI) and the bowel from computed tomography (CT) images. Stomach MR images from 116 patients undergoing 0.35T MRI-guided abdominal radiotherapy and bowel CT images from 120 patients undergoing high dose rate pelvic brachytherapy treatment were collected. For each patient volume, the manual delineation of the HDO was extracted from every 8th slice. These manually drawn contours were first interpolated to obtain an initial estimate of the HDO contour. A two-channel 64×64pixel patch-based convolutional neural network (CNN) was trained to localize the position of the organ's boundary on each slice within a five-pixel wide road using the image and interpolated contour estimate. This boundary prediction was then input, in conjunction with the image, to an organ closing CNN which output the final organ segmentation. A Dense-UNet architecture was used for both networks. The MAI algorithm was separately trained for the stomach segmentation and the bowel segmentation. Algorithm performance was compared against linear interpolation (LI) alone and against fully automated segmentation (FAS) using a Dense-UNet trained on the same datasets. The Dice Similarity Coefficient (DSC) and mean surface distance (MSD) metrics were used to compare the predictions from the three methods. Statistically significance was tested using Student's t test. For the stomach segmentation, the mean DSC from MAI (0.91 ± 0.02) was 5.0% and 10.0% higher as compared to LI and FAS, respectively. The average MSD from MAI (0.77 ± 0.25mm) was 0.54 and 3.19mm lower compared to the two other methods. Only 7% of MAI stomach predictions resulted in a DSC<0.8, as compared to 30% and 28% for LI and FAS, respectively. For the bowel segmentation, the mean DSC of MAI (0.90 ± 0.04) was 6% and 18% higher, and the average MSD of MAI (0.93 ± 0.48mm) was 0.42 and 4.9mm lower as compared to LI and FAS. Sixteen percent of the predicted contour from MAI resulted in a DSC<0.8, as compared to 46% and 60% for FAS and LI, respectively. All comparisons between MAI and the baseline methods were found to be statistically significant (p-value<0.001). The proposed MAI algorithm significantly outperformed LI in terms of accuracy and robustness for both stomach segmentation from low-field MRIs and bowel segmentation from CT images. At this time, FAS methods for HDOs still require significant manual editing. Therefore, we believe that the MAI algorithm has the potential to expedite the process of HDO delineation within the radiation therapy workflow.

Comparative dosimetry of brachytherapy treatment planning between a volume-based plan by CT and a point-based plan by TAUS in CT datasets for brachytherapy

Abstract Aim: To evaluate comparative dosimetry of brachytherapy treatment planning between a volume-based plan by computed tomography (CT) and a point-based plan by transabdominal ultrasound (TAUS) in CT datasets for brachytherapy. Materials and methods: From 2019 to 2021, 59 different datasets of CT images were collected from 38 patients treated by intracavitary brachytherapy with tandem ovoid or tandem ring applicators. At that time, TAUS was performed to prevent uterine perforation and to evaluate topography of the cervix during application. In volume-based planning by CT, the target dose was used to keep the dose at 90% of high-risk clinical target volume (HR-CTV), to give a dose of at least 7Gy, while in the point-based plan by TAUS, the target dose was used to keep the minimum dose to eight cervix reference points (measured by TAUS), to give a dose of at least 7Gy. The doses to targets and organs at risk were evaluated and compared between volume-based planning by CT and the point-based plan by TAUS. Results: Of 59 fractions, a tandem ovoid applicator was used in 48 fractions (81·3%). In the volume-based plan by CT, the mean doses to HR-CTV(D90), intermediate-risk clinical target volume (IR-CTV)(D90), bladder(D2cc), rectum(D2cc) and sigmoid colon(D2cc) were 7·0, 3·9, 4·9, 2·9 and 3·3 Gy, respectively, while in the point-based plan by TAUS, the mean doses to HR-CTV(D90), IR-CTV(D90), bladder(D2cc), rectum(D2cc) and sigmoid colon(D2cc) were 8·2, 4·6, 5·9, 3·4 and 3·9 Gy, respectively. The percentages of mean dose differences between TAUS and CT of HR-CTV(D90), IR-CTV(D90), bladder(D2cc), rectum(D2cc) and sigmoid colon(D2cc) were 17·7, 19·5, 20·5, 19·5, 21·3 and 19·8%, respectively. With the target dose to the point-based plan by TAUS (7 Gy to the cervix reference points), this was close to D98 of HR-CTV with a mean percentage of difference of 0·6%. Findings: The point-based plan by TAUS showed higher values to targets and organs at risk than the volume-based plan by CT. With the point-based plan by TAUS, it was close to D98 of HR-CTV.

Recent Advances in Brachytherapy Using Radioactive Nanoparticles: An Alternative to Seed-Based Brachytherapy

Interstitial brachytherapy (BT) is generally used for the treatment of well-confined solid tumors. One example of this is in the treatment of prostate tumors by permanent placement of radioactive seeds within the prostate gland, where low doses of radiation are delivered for several months. However, successful implementation of this technique is hampered due to several posttreatment adverse effects or symptoms and operational and logistical complications associated with it. Recently, with the advancements in nanotechnology, radioactive nanoparticles (radio-NPs) functionalized with tumor-specific biomolecules, injected intratumorally, have been reported as an alternative to seed-based BT. Successful treatment of solid tumors using radio-NPs has been reported in several preclinical studies, on both mice and canine models. In this article, we review the recent advancements in the synthesis and use of radio-NPs as a substitute to seed-based BT. Here, we discuss the limitations of current seed-based BT and advantages of radio-NPs for BT applications. Recent progress on the types of radio-NPs, their features, synthesis methods, and delivery techniques are discussed. The last part of the review focuses on the currently used dosimetry protocols and studies on the dosimetry of nanobrachytherapy applications using radio-NPs. The current challenges and future research directions on the role of radio-NPs in BT treatments are also discussed.

Chinese Expert Consensus on Iodine125 Seed Implantation for Recurrent Cervical Cancer in 2021.

The treatment modality for recurrent cervical cancer (rCC) is limited, and the prognosis of these patients is poor. Seed implantation could be an important component of rCC management in the context of dose boost or salvage therapy after surgery or radiotherapy, which is characterized by a minimally invasive, high local dose, and rapidly does fall, sparing normal tissue. For patients with good performance status and lateral pelvic wall recurrence with an available puncture path, seed implantation was recommended, as well as for selected central pelvic recurrence and extra-pelvic recurrence. The combination of brachytherapy treatment planning system and CT guidance was needed, and three-dimensional printing templates could greatly improve the accuracy, efficiency, and quality of seed implantation to achieve a potential ablative effect and provide an efficient treatment for rCC. However, the recommendations of seed implantation were mainly based on retrospective articles and lack high-quality evidence, and multicenter prospective randomized studies are needed. In this consensus on iodine125 seed implantation for rCC, indication selection, technical process and requirements, dosimetry criteria, radiation protection, combined systemic therapy, and outcomes of seed implantation for rCC are discussed.

Comparison of iodine-125 plaque brachytherapy and gamma knife stereotactic radiosurgery treatment outcomes for uveal melanoma patients.

To compare the efficacies of iodine-125 brachytherapy (IBT) and gamma knife stereotactic radiosurgery (GKRS) in the treatment of posterior uveal melanoma. The demographic data and tumor characteristics at diagnosis of 201 patients treated with IBT and 52 patients treated with GKRS were recorded. The two treatments were then compared in terms of complications, local control, eye retention, metastasis, and overall survival rate. The median follow-up time was 56months for the GKRS group and 45months for the IBT group (p = 0.167). There were no significant differences in demographic data or tumor characteristics between the groups at diagnosis. Radiation retinopathy, radiation optic neuropathy, and neovascular glaucoma occurred at similar rates in both groups. However, radiation maculopathy and cataracts occurred more frequently in the GKRS group. The number of cases that have developed vision loss (worsening of best-corrected visual acuity on three or more lines on the Snellen chart) was significantly higher in the GKRS group (60%) compared to the IBT group (44%) (p = 0.048). Local control, metastasis, and 5-year overall survival rates were statistically similar in both groups. GKRS can be preferred as an eye-sparing treatment option for posterior uveal melanoma in cases where brachytherapy cannot be used.

Usefulness of Vaginal/Rectal Cylinders or Interstitial Needles for Dosimetric Verification and Uncertainty Analysis of Brachytherapy Treatment

Usefulness of Vaginal/Rectal Cylinders or Interstitial Needles for Dosimetric Verification and Uncertainty Analysis of Brachytherapy Treatment

Clinical and Genomic Determinants of Survival in Ugandan Women With Cervical Cancer

Clinical and Genomic Determinants of Survival in Ugandan Women With Cervical Cancer

Pilot Study to Assess the Change in Vaginal Dimensions Following Vaginal Brachytherapy (VBT)

Toxicities related to vaginal brachytherapy can be challenging to capture in patients with endometrial cancer treated with VBT HDR. In this pilot study, we sought to objectively measure the changes in vaginal length and caliber while capturing patient reported acute and chronic toxicities.63 patients with endometrial carcinoma treated with VBT 30 Gy in 3 fractions to the vaginal surface using Ir192 HDR from March 2015 through December 2018 were invited to return for a research visit. 18 patients with AJCC 8th pT1-T2 pNx-N1 cM0 endometrial carcinoma returned to clinic for measurement of vaginal length and diameter using VBT cylinders. Measurements were compared to vaginal length/diameter assessed during the first brachytherapy treatment. Vaginal and vulvar atrophy were assessed. Pain during insertion was measured on a scale of 0 to 10. The patients completed questionnaires regarding vaginal, rectal, urinary and dermatologic toxicities (using CTCAE v5.0). Toxicities were classified as acute if they occurred within the first 2 months after treatment, or chronic if they occurred 2 months after treatment. The mean differences in change between start of VBT and research visit for both vaginal length and diameter were calculated.Median age at time of diagnosis was 69 years (range 46-88). Tumor stage was pT1a 50% (n = 9), pT1b 38.9% (n = 7), and pT2 11.1% (n = 2). Of the 18, 13 (72.2%) had endometrioid tumors, 2 (11.1%) had serous, 2 (11.1%) had mixed, and 1 (5.6%) had clear cell. Median length of time from VBT start until research visit was 43.3 months. The median original vaginal length of the 18 women was 13.9 cm (range 11 - 18 cm). The median original cylinder size was 3.0 cm (range 2.5-3.0 cm). The mean decrease in vaginal length from VBT start to visit date was 1.4 cm, which was significantly different from zero (P = 0.0002). The mean decrease for the vaginal diameter was 0.03 cm which was not significantly different from zero (P = 0.6). On exam, 12 (66.6%) had grade 1-2 vaginal atrophy and 5 (27.8%) had grade 1 vulvar atrophy. Pain during cylinder placement was median of 1 (range 0-10); 77.8% had 0-2 out of 10 pain. Patient-reported acute grade 1-2 toxicities included dermatitis (n = 1), and cystitis (n = 1). There were no patient-reported grade 3-5 acute or chronic toxicities. Patient-reported chronic grade 1-2 toxicities included cystitis (n = 2), vaginal stenosis (n = 2), and diarrhea (n = 1).In our pilot study of 18 patients treated with VBT with 30 Gy in 3 fractions to the vaginal surface, we found a statistically significant average vaginal shortening after approximately 4.5 years of average follow-up. We observed no significant change in vaginal diameter. VBT was followed by infrequent patient-reported grade 1-2 acute or chronic toxicities. This report adds to the scarce literature of objective data on vaginal sequelae of VBT for endometrial carcinoma.K. Nieto: None. B. Levine: None. D.R. Brown: None. H.S. McGinnis: None. C.M. Lanier: None. K. Hines: None. K.M. Greven: None.