Gastrointestinal and genitourinary toxicity following high dose rate vaginal cuff brachytherapy for endometrial...

There are currently no organs at risk dose constraints for adjuvant HDR vaginal cuff brachytherapy (VBT). This study evaluates OAR dosimetry and the association with acute and chronic gastrointestinal (GI) or genitourinary (GU) toxicity.

Patients treated at a single institution with VBT of 21 Gray (Gy) in 3 fractions (Fx) prescribed to 5 mm depth twice weekly and CT-based 3D planning were reviewed. OAR doses (D2cc, D1cc, and D0.1cc) were recorded. Acute and chronic toxicities were graded by Common Terminology Criteria for Adverse Events v5.0. Boxplot and Wilcoxon-Mann-Whitney tests compared dose thresholds.

177 patients with stage I-IV endometrial cancer received a mean D2cc to rectum, sigmoid, small bowel, and bladder of 5.7 Gy (range: 2.8-8.7), 3.3 Gy (0.6-9.3), 3.8 Gy (0.0-9.1), and 5.4 Gy (2.0-8.2). Overall, 6.2% (n = 11) and 7.3% (n = 13) of patients experienced acute GI and GU toxicity of any grade. 14.7% (n = 26) and 14.7% (n = 26) of patients experienced chronic GI and GU toxicity of any grade, respectively. There were two grade 3 toxicities include one chronic GI and one acute GU. No dosimetric factors were identified that correlated with a higher likelihood of acute or chronic toxicity.

The overall rate of GI and GU toxicity following VBT of 21 Gy in 3 Fx is low, and there are no dosimetric parameters that correlate with toxicity. The optimal dose fractionation schedule that balances high local control with minimal toxicity is yet to be determined.