325 - Moderately Hypofractionated Online Adaptive Definitive Chemoradiotherapy for Cervical Cancer: Updated 2-Year Outcomes from a Prospective Institutional Study

Purpose/Objective(s): This study evaluated the long-term feasibility, efficacy, and safety of moderately hypofractionated online adaptive definitive chemoradiotherapy for cervical cancer based on updated 2-year follow-up data.

Materials/Methods: In this prospective institutional study, patients with biopsy-confirmed cervical cancer undergoing definitive treatment were consecutively enrolled. All patients received moderately hypofractionated online adaptive radiotherapy (oART) guided by iterative cone-beam CT (iCBCT). Pelvic external beam radiotherapy (EBRT) was delivered to 43.35 Gy in 17 fractions, with a simultaneous integrated boost of 54.40 Gy in 17 fractions to radiographically involved lymph nodes. Target volumes were delineated and adapted daily according to anatomical changes observed on iCBCT . Image-guided three-dimensional high-dose-rate brachytherapy (30 Gy in 5 fractions) followed external beam treatment. Concurrent weekly cisplatin was administered throughout radiotherapy. Tumor response was assessed using RECIST version 1.1. Acute and late toxicities were graded according to CTCAE version 5.0. Patient-reported quality of life was evaluated using the EORTC QLQ-C30 and QLQ-CX24 questionnaires.

Results: Thirty patients completed 510 fractions of oART with concurrent chemotherapy. The mean treatment time per fraction was 23 minutes and 18 seconds. Adaptive plans achieved superior target coverage and improved organ-at-risk sparing compared with scheduled plans. The median EBRT duration was 22 days, with a median overall treatment time of 43 days. At completion of EBRT, the mean tumor regression rate was 83.3%, and the complete response rate at 3 months was 100%. The 2-year overall survival, disease-free survival, and local control rates were 100%, 93.3%, and 100.0%, respectively. Grade 3 acute gastrointestinal toxicity occurred in 10% of patients and resolved within 2 days; no grade 3 acute genitourinary toxicity was observed. No grade =3 late toxicities occurred. Late grade 2 gastrointestinal and genitourinary toxicities were observed in 16.7% and 6.7% of patients, respectively. Quality of life declined during EBRT but exceeded baseline levels 4 months after treatment.

Conclusion: With updated 2-year follow-up, moderately hypofractionated online adaptive definitive chemoradiotherapy demonstrated durable tumor control, minimal high-grade toxicity, and recovery of quality of life. These findings support its feasibility and safety as an efficient definitive treatment strategy for cervical cancer.