1084 - A Prospective Single-Arm Study of Daily Online Adaptive Radiotherapy for Cervical Cancer with Reduced PTV Margin: Acute Toxicity Results

G. Wang¹, J. Yan², Y. Chen³, J. Qiu², and F. Zhang¹; ¹Department of radiation oncology, Peking Union Medical College Hospital. Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China, ²Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China, ³Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100730, China, Beijing, China

Purpose/Objective(s): To evaluated acute toxicity in cervical cancer treated with daily iterative cone-beam computed tomography (iCBCT)-guided online adaptive radiotherapy (oART) using reduced plannning target volume (PTV) margin. Materials/

Methods: We prospectively enrolled patients with stage I-III cervical cancer in a single-arm study. All patients received daily iCBCT-guided oART (50.4Gy/ 28f) with concurrent weekly chemotherapy, followed by CT/MR-guided intracavitary brachytherapy(30Gy/ 5f). A uniform 10 mm margin was used to cover more variable uterus (PTV-U), and 5 mm margin was used for other PTV. Acute toxicities (within 90 days after initiation of radiotherapy) were assessed before treatment, weekly during treatment, and 1 month after treatment, and graded according to the CTCAE 5.0. Patient-reported acute toxicity was derived from the EORTC Quality of Life Questionnaire (QLQ)-C30 questionnaire.
Results: From February 2023 to November 2023, 30 patients completed anticipated protocol treatment, but 3 patients had protocol violations during follow-up. A total of 27 patients were analyzed and the follow-up rate of acute toxicity was 100%. A comprehensive review one month after treatment showed complete tumor regression, and as of the last follow-up three months after treatment, no patient had local recurrence or distant metastasis. Overall, no patient had Grade = 4 acute toxicities. Grade 1, 2, and 3 acute hematological toxicities were 15% (4 cases), 33% (9 cases), and 22% (6 cases), respectively. The most common gastrointestinal toxicity was diarrhea, with Grade 1, 2, and 3 diarrhea occurring in 22% (6 cases), 15%, and 4%, respectively. The acute gastrointestinal toxicity of Grade 1, 2 and 3 were 26% (7 cases), 19% (5 cases), and 4%, respectively. Only 7% (2 cases) had Grade 1 acute genitourinary toxicity, presented as urinary tract pain and vaginal discharge, and no Grade 2 or above toxicities occurred. The symptoms were relieved during brachytherapy, and no Grade 2 or above symptoms occurred. At 1 months after treatment, only one patient had Grade 1 diarrhea and one patient had Grade 1 anemia. For patient-reported toxicities, mean scores in the functioning scales significantly decreased and mean scores in the symptom scales significantly increased after oART initiation. Improvement began during the brachytherapy period and basically returned to the baseline level at 1 month after treatment.
Conclusion: Our results supported the hypothesis that daily oART using reduced PTV margin could reduce the acute toxicity for cervical cancer. Table. The mean scores of the QLQ-C30. p1, p2 values present before oART vs. 1 month after treatment, and before oART vs. oART.

	before oART	oART	brachytherapy	1 months after treatment	p1	p2
Functioning scale
Physical	92.5	79.25	80.29	92.27	0.048	<0.01
Global quality of life	73.26	60.82	67.93	81.33	0.281	0.007
Symptom scale
Fatigue	21.76	34.99	27.78	14.22	0.539	<0.01
Nausea and vomiting	3.47	18.78	8.33	1.33	0.095	<0.01
Diarrhoea	1.39	22.39	11.59	2.67	0.596	<0.01