Late course adaptive radiotherapy based on tumor volume reduction decreases Gastrointestinal toxicity for abdominal lymph node metastasis of hepatocellular carcinoma

This study aimed to quantify tumor volume reduction during radiotherapy for abdominal lymph node metastases (LNM) of hepatocellular carcinoma (HCC) and assess the potential benefits of late-course adaptive radiotherapy. Forty HCC Patients with abdominal LNM treated from January 2021 to March 2024 received radiotherapy in combination with targeted therapy or immunotherapy. Second simulation scan was performed during the fourth week of radiotherapy. Two-thirds of patients underwent redesigned radiotherapy plan as the test group, while remaining patients continued with the original plan as the control group. Dose-volume metrics for organs at risk and toxicities were compared. At the time of second scan, median radiotherapy dose administered to all patients was 38.0 Gy. Mean tumor volume reduction was 56.20cc (95% CI 35.20-77.21cc) and 29.65% (95% CI 24.49%-34.80%). Irradiation dose and volume to stomach, small intestine, colon, liver, and kidneys were significantly reduced in test group. Meanwhile, gastrointestinal toxicities were notablely decreased, including dyspepsia (P = 0.018), nausea (P = 0.013), vomiting (P = 0.041), and diarrhea (P = 0.040). Tumor regression during radiotherapy for abdominal LNM of HCC is significant. A second simulation scan performing when the irradiation dose reaches approximately 40 Gy and applying adaptive radiotherapy in the late course can enhance irradiation accuracy and reduce toxicities.