Clinical outcomes of abbreviated high dose-rate brachytherapy in locally advanced cervical cancer: lessons from the COVID pandemic for high dose-rate fractionation.

Purpose: To evaluate outcomes of cervical cancer patients treated with abbreviated high dose rate brachytherapy (HDR-BT) that used 2-implants and delivered 4-5 fractions over 7-12 days rather than 21-28 days.

Materials and methods: Patients with stage IB2-IVA cervical cancer, treated with external beam radiation (EBRT) ± chemotherapy followed by abbreviated MR/CT-based HDR-BT were included. The planning aim was to achieve > 70Gy equivalent doses in 2Gy (EQD2_10Gy) at Point A dose in patients undergoing intracavitary BT (ICBT) and > 85Gy EQD2_10Gy to the HRCTV in intracavitary-interstitial BT (IC-ISBT). The dose constraints to 2 cc of bladder, rectum and sigmoid were restricted to < 90Gy₃, < 75Gy₃ and < 75Gy EQD2_3Gy respectively.

Results: From 2020 to 2022, 245 patients were treated with EBRT followed by MR/CT-based HDR-BT. Median OTT was 57 days. The median HRCTV volume was 35.5cc with higher HRCTV in MR than CT-based (42.3cc vs. 32.8cc). The median dose to Point-A, HRCTV-D90, B2cc, R2cc and S2cc for ICBT was 78.1, 86.2, 87, 70.2 and 70.4Gy respectively. For IC-ISBT cohort, the median dose to HRCTV-D90, B2cc, R2cc, and S2cc was 86.1, 88.6, 70 & 66.7Gy respectively. The 3-years local control, pelvic control, locoregional, disease free and overall survival was 90%, 88%, 83.7%, 75.5% and 85% respectively. Late ≥ grade III gastrointestinal and genitourinary toxicities were 7.3% and 1.6% respectively with marginally higher toxicity in CT based cohort.

Conclusion: Accelerated HDR-BT schedule of 2-implants 4-5 fractions is radiobiological iso-effective and clinically safe with comparable oncological outcomes and adverse events.