PO38

Abstract

Purpose Adjuvant vaginal cuff brachytherapy (VCB) for endometrial cancer (EC) is typically delivered with single-channel vaginal cylinders with diameters ranging from 2.0 to 4.0 cm. Due to the unfavorable dosimetry of 2.0 cm diameter cylinders, larger diameter cylinders are used whenever possible. There are, however, occasional patients with narrow vaginal anatomy for whom only a 2.0 cm cylinder can be accommodated. In this unique population, in addition to the dosimetric challenges for a typical prescription to 5 mm depth (ie., heterogeneity of about 170% and 210% of prescription dose at the surface of the cylinder lateral walls and tip, respectively), there tend to be clinical challenges as well such as insertional pain or difficulty with procedural tolerance. This study reports the clinical outcomes of an EC cohort that received VCB with cylinder size 2.0 cm at a single institution. Materials and Methods From an IRB-approved institutional database of EC patients treated with VCB between 07/01/2014-11/30/2022, all patients that were fitted with 2.0 cm cylinder were retrospectively reviewed. Although our institutional prescriptions for cylinders larger than 2.0cm are at 5mm depth (6-7 Gy x 3 fractions weekly), for the 2.0cm cylinder patients, VCB prescriptions are to the vaginal surface (10Gy x 3 fractions weekly), to avoid issues resulting in unacceptably high surface dose. Patient demographics, disease and treatment characteristics, recurrence rates and complications were descriptively analyzed. Toxicity was recorded via the CTCAE v4.0. The Kaplan-Meier method was used to assess freedom from vaginal recurrence. All computations were performed in IBM SPSS Statistics 28. Results Among 655 consecutive EC patients treated with VCB, there were 36 women (5%) that were treated with cylinder size 2.0 cm. Median age was 68.5 years (range: 46-95 years). The majority were nulliparous (77.8%) and 15 women (42%) had documented baseline pain or anxiety related to pelvic examination prior to VCB. Median BMI was 39 (range: 19-62). Baseline vaginal length was 8.3cm (range: 5-14cm). 78% had stage I-II, 14% had stage IIIA, and 8% had stage IVB EC. The histological subtypes included endometrioid adenocarcinoma (69%), mixed (11%), serous (8%), clear cell (6%) and de-differentiated (6%). 42% of the patients received chemotherapy. None received external beam radiotherapy. Median interval from surgery to VCB was 54 days (range: 43-119 days). All received 10Gy x 3 fractions prescribed to vaginal surface, and active length was 3cm (5.6%), 4cm (63.9%) or 5cm (30.6%). 3D planning was performed in 58% of the cohort, while 2D planning was used in the remainder due to issues related to body habitus and/or poor mobility. Median follow-up was 17.5 months (range: 3-76 months). The 2-year freedom from vaginal recurrence was 96%. There was only 1 vaginal recurrence, which was out of field. 5 patients died from disease, unrelated to radiation treatment. There were no grade 2 or higher gastrointestinal or urinary toxicities recorded in the follow-up period. 50% of patients were compliant with dilators and of those that had prospective measurement of vaginal stenosis in the follow-up period (n=19), 79% had grade 0 or 1, 21% had grade 2, and 0% had grade 3. Conclusions The 2.0 cm diameter cylinder was used in only 5% of EC patients treated with VCB at our institution. Among this population with unique dosimetric and clinical concerns, the regimen of 10 Gy x 3 fractions prescribed to vaginal surface was well-tolerated with no adverse outcomes and excellent local control. Adjuvant vaginal cuff brachytherapy (VCB) for endometrial cancer (EC) is typically delivered with single-channel vaginal cylinders with diameters ranging from 2.0 to 4.0 cm. Due to the unfavorable dosimetry of 2.0 cm diameter cylinders, larger diameter cylinders are used whenever possible. There are, however, occasional patients with narrow vaginal anatomy for whom only a 2.0 cm cylinder can be accommodated. In this unique population, in addition to the dosimetric challenges for a typical prescription to 5 mm depth (ie., heterogeneity of about 170% and 210% of prescription dose at the surface of the cylinder lateral walls and tip, respectively), there tend to be clinical challenges as well such as insertional pain or difficulty with procedural tolerance. This study reports the clinical outcomes of an EC cohort that received VCB with cylinder size 2.0 cm at a single institution. From an IRB-approved institutional database of EC patients treated with VCB between 07/01/2014-11/30/2022, all patients that were fitted with 2.0 cm cylinder were retrospectively reviewed. Although our institutional prescriptions for cylinders larger than 2.0cm are at 5mm depth (6-7 Gy x 3 fractions weekly), for the 2.0cm cylinder patients, VCB prescriptions are to the vaginal surface (10Gy x 3 fractions weekly), to avoid issues resulting in unacceptably high surface dose. Patient demographics, disease and treatment characteristics, recurrence rates and complications were descriptively analyzed. Toxicity was recorded via the CTCAE v4.0. The Kaplan-Meier method was used to assess freedom from vaginal recurrence. All computations were performed in IBM SPSS Statistics 28. Among 655 consecutive EC patients treated with VCB, there were 36 women (5%) that were treated with cylinder size 2.0 cm. Median age was 68.5 years (range: 46-95 years). The majority were nulliparous (77.8%) and 15 women (42%) had documented baseline pain or anxiety related to pelvic examination prior to VCB. Median BMI was 39 (range: 19-62). Baseline vaginal length was 8.3cm (range: 5-14cm). 78% had stage I-II, 14% had stage IIIA, and 8% had stage IVB EC. The histological subtypes included endometrioid adenocarcinoma (69%), mixed (11%), serous (8%), clear cell (6%) and de-differentiated (6%). 42% of the patients received chemotherapy. None received external beam radiotherapy. Median interval from surgery to VCB was 54 days (range: 43-119 days). All received 10Gy x 3 fractions prescribed to vaginal surface, and active length was 3cm (5.6%), 4cm (63.9%) or 5cm (30.6%). 3D planning was performed in 58% of the cohort, while 2D planning was used in the remainder due to issues related to body habitus and/or poor mobility. Median follow-up was 17.5 months (range: 3-76 months). The 2-year freedom from vaginal recurrence was 96%. There was only 1 vaginal recurrence, which was out of field. 5 patients died from disease, unrelated to radiation treatment. There were no grade 2 or higher gastrointestinal or urinary toxicities recorded in the follow-up period. 50% of patients were compliant with dilators and of those that had prospective measurement of vaginal stenosis in the follow-up period (n=19), 79% had grade 0 or 1, 21% had grade 2, and 0% had grade 3. The 2.0 cm diameter cylinder was used in only 5% of EC patients treated with VCB at our institution. Among this population with unique dosimetric and clinical concerns, the regimen of 10 Gy x 3 fractions prescribed to vaginal surface was well-tolerated with no adverse outcomes and excellent local control.