Use of a vaginal dilator during chemoradiation for anal cancer to mitigate toxicity.

Abstract

9 Background: Women with anal cancer are at risk of developing urinary and sexual treatment-related toxicity due to radiation (RT) dose to bladder, vagina, erectile tissue, and urethra. When used during radiotherapy, vaginal dilators decrease the risk of vaginal stenosis by decreasing dose to the anterior vaginal wall. The potential benefits of vaginal dilator use in sparing other pelvic organs at risk are poorly defined. Methods: We performed a single-institution retrospective review of women treated with chemoRT for anal cancer between 2012-2025. Patients were categorized by use of a vaginal dilator during treatment. Bladder, bulboclitoris, vagina, genitalia and urethra were contoured according to published atlases. Dosimetric analysis was performed to compare RT dose to all structures with or without a vaginal dilator. Urinary side effects were retrospectively graded according to CTCAEv5, and the rate of grade 2+ urinary toxicity was compared between groups using a Chi-square test. RT dose to the organs at risk was compared between the groups using independent sample t-tests. Results: Forty-nine patients were included in this analysis and 11 (22%) were treated with a vaginal dilator. Most patients had Stage II (37%) or Stage III (49%) disease and there was no difference in disease stage distribution between the groups (p=0.5). The median dose to primary tumor was 54 Gy for patients treated without a dilator versus 50.4 Gy in those treated with a dilator (p=0.25). Use of a vaginal dilator during RT led to significantly less dose to the bladder, bulboclitoris and urethra (Table). Dose to the genitalia was not significantly different between the two groups. Eleven patients (29%) treated without a vaginal dilator had grade 2+ urinary toxicity compared to one patient (9%) treated with a vaginal dilator (p=0.18). Conclusions: Vaginal dilators can be used to decrease dose to bladder, bulboclitoris and urethra when treating women with chemoRT for anal cancer. The data suggests that vaginal dilator use during RT may decrease rates of urinary and sexual toxicity. These findings should be confirmed in a larger cohort of patients with patient-reported outcome metrics. Organ Without Vaginal Dilator With Vaginal Dilator p-value Bladder Mean (Gy) 30.1 20.6 0.58 Bulboclitoris Mean (Gy) V30 (cc) V40 (cc) 36.912.69.0 27.75.54.0 0.020.04<0.01 Genitalia Mean (Gy) 19.2 15.6 0.32 Urethra Mean (Gy) V20 (cc) V30 (cc) 44.56.15.6 19.93.90.8 <0.010.02<0.01