2811 - 3D Imaging Analysis of Changes in Vaginal Dimensions After Pelvic Radiotherapy

Purpose/Objective(s): Pelvic radiotherapy (RT) is associated with vaginal shortening, narrowing, reduced elasticity, and fibrosis. The vagina is a critical organ of interest (OOIs) within or close to the target areas of high-dosage RT. Early detection of vaginal morphology changes after RT is crucial as radiation-induced changes may have negative impacts on sexual function, vaginal health, and clinical exams. Our objective was to assess the effects of RT on vaginal dimensions using a novel 3D approach. We hypothesize decreased vaginal width and length post-RT.

Materials/Methods: We conducted a retrospective cohort study of adult female pelvic cancer survivors who completed pelvic RT =1 year before enrollment. Pelvic magnetic resonance images (MRIs) pre-RT and 4-10 months post-RT were collected. The vagina was contoured (with the vaginal wall/lumen as a single structure) on MRI to create 3D models. 3D vaginal models were iteratively sliced axially to identify the vaginal centerline and lateral margins. Vaginal length (centerline length), maximum transverse width (largest left-to-right margin distance), surface area, and volume were measured. Wilcoxon Signed-Rank tests evaluated differences in vaginal dimensions pre- vs post-RT.

Results: 9 adult female cancer survivors were included. The majority were postmenopausal (78%). Median age, BMI, vaginal parity, and months post-RT were 57 years (IQR 47-66), 27.1 kg/m2 (IQR 24-30), 1 (IQR 0-3), and 5.2 months (IQR 5-7), respectively. Cancer cases were 6 anal (66%), 1 rectum (11%), 1 uterine (11%), and 1 cervical (11%). 8 (88%) received external beam radiotherapy (EBRT) and 1 (11%) brachytherapy (BT). The mean cumulative prescribed dose was 5948.4 cGy EQD2(10) (SD: . After RT, the vaginal maximum transverse width decreased by 7.5 mm (p=0.03) as demonstrated by Table 1. Vaginal length, surface area, and volume also decreased, but differences were not statistically significant.

Conclusion: This study is the first 3D imaging-based analysis to quantify vaginal dimension changes post-RT. Knowledge of how female sexual OOIs change after radiation may serve as early indicators, helping clinicians implement earlier interventions and counsel patients on managing late effects. Further research is warranted to correlate the changes with dose metrics in hopes of establishing dose guidance for sexual OOIs, refining radiation planning to mitigate sexual dysfunction and improve vaginal health for survivors.