221 - Feasibility of Moderately Hypofractionated Online Adaptive Radiotherapy in the Treatment of Cervical Cancer
Presenter(s)
Z. Zeng1, Z. Wang1, J. Yan2, K. Hu3, and F. Zhang2; 1Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China, 2Department of Radiation Oncology, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China, 3Peking Union Medical College Hospital, Beijing, China
Purpose/Objective(s): This study aims to explore the feasibility of moderately hypofractionated online adaptive radiotherapy (oART) for cervical cancer. It evaluates the quality of the treatment process, including target dose coverage, organs at risk (OARs) dose reduction, treatment time efficiency, and treatment completion rate.
Materials/Methods:
This prospective clinical study included cervical cancer patients who underwent concurrent chemoradiotherapy between September 2023 and April 2024. A total of 30 patients were enrolled. Participants received daily oART, with 43.35 Gy delivered in 17 fractions to the clinical target volume and a simultaneous integrated boost of 54.40 Gy in 17 fractions to the gross lymph nodes. The treatment was administered using the Ethos platform for oART, guided by iterative cone beam computed tomography (iCBCT). The study employed an online adaptive workflow, involving iCBCT scans for image acquisition, artificial intelligence-assisted contouring, plan adaptation, and treatment verification. Time for each process was tracked, and dosimetric assessments were performed to evaluate target volume coverage and OARs protection. Treatment completion rate was reported.Results:
The treatment was successfully implemented for 510 sessions of oART in 30 patients, with a 99.0% success rate for the first oART adaptation. The average time required for each treatment fraction was 23 minutes and 18 seconds, with the adaptive workflow (from the first iCBCT scan to selecting the adapted plan) taking an average of 17 minutes and 20 seconds. The adapted plan was selected in 99.4% of fractions and significantly improved the dosimetric coverage (V100%, V98%, V95%, V90%) for CTV and PTV, especially V100% for PTV of the uterus and PTV of the cervix, which improved by nearly 7.26% and 8.79%, respectively (P < 0.001). The adapted bladder Dmean was 161.71 cGy, the rectum Dmean was 181.76 cGy, and the small bowel Dmean was 123.24 cGy, significantly lower than the scheduled plan values of 166.00 cGy, 202.53 cGy, and 134.18 cGy, respectively. The V10, V20, V30, and V40 for the small bowel, rectum, and bladder also showed significant reduction. The dosimetry for the bone marrow and femoral heads was also improved with adaptation.Conclusion: This first clinical experience with moderately hypofractionated oART for cervical cancer demonstrates its feasibility. The study highlights improved target coverage, reduced OAR doses, and efficient treatment time. These findings suggest that oART can enhance treatment quality, making it a promising approach for cervical cancer. (NCT05994300)