Presenter(s)
B. Wang1,2, N. Siah1,2, J. Han1,2, Z. Diao3, and S. Zhang4,5; 1Cancer Center, Hubei Key Laboratory of Precision Radiation Oncology,Institute of Radiation Oncology,Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, China, 2Key Laboratory of Biological Targeted Therapy(Huazhong University of Science and Technology), Ministry of Education, Wuhan, Hubei 430022, China, 3Wuhan United Imaging Healthcare Co., Ltd, Wuhan, Hubei, China, 4Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430023, China, 5Key Laboratory of Biological Targeted Therapy(Huazhong University of Science and Technology), Ministry of Education, Wuhan, China
Purpose/Objective(s):
Given substantial interfraction anatomical variation in esophageal cancer, we evaluated whether clinically implemented weekly online adaptive radiotherapy (ART) improves target coverage and organ-at-risk sparing compared with non-adaptive image-guided radiotherapy (IGRT).Materials/Methods:
Fourteen patients with middle-distal or distal esophageal cancer treated at our center were retrospectively analyzed. Prescribed doses ranged from 40-60 Gy in 20-30 fractions. All patients were treated on a fan-beam CT (FBCT)–guided linear accelerator providing diagnostic-quality imaging for precise target delineation and dose calculation. Unlike conventional CBCT, this enables accurate target delineation for esophageal cancer and precise dose calculation. Weekly online ART was performed: following patient setup, FBCT acquisition, target and OAR re-contouring, plan re-optimization, and quality assurance were completed within 13-18 minutes. Dosimetric parameters including target coverage (PTV D95%), dose heterogeneity (PTV D1%), lungs V5Gy/V20Gy, and heart mean dose were compared between the scheduled plans (non-adaptive IGRT) and the adapted plans (online ART). PTV D95%/D1% were normalized to individual prescription doses.Results:
GTVp volumes fluctuated during early treatment due to chemoradiation-induced edema but showed overall regression. Without ART, reliable target coverage was difficult to maintain due to tumor motion from lung and gastrointestinal dynamics. ART significantly improved target coverage (mean normalized PTV D95%: 101.0% vs. 96.2% with scheduled plans, p<0.001) and reduced dose heterogeneity (mean normalized PTV D1%: 107.4% vs. 109.1%, p=0.032). One patient showed dramatic improvement, with normalized D95% increasing from 79.5% to 101.2%. ART also demonstrated substantial OAR sparing: mean lung V5Gy decreased from 37.5% to 35.4% (p=0.018), V20Gy from 13.3% to 11.6% (p=0.042), and heart mean dose from 1886.5 cGy to 1775.6 cGy (p=0.047). Patients with the largest anatomical variations derived the greatest benefit.Conclusion:
Online ART significantly restores target coverage and reduces OAR exposure compared with scheduled IGRT in middle-distal esophageal cancer. Weekly FBCT-guided adaptation effectively compensates for interfraction anatomical variation and mitigates the risk of geographic miss. The clinically implemented workflow was feasible within a 13–18-minute timeframe, and the use of a low-dose FBCT protocol (approximately 1/4–1/2 the dose of kV-CBCT) supports safe and practical clinical implementation. Patients with substantial anatomical changes derived the greatest benefit, supporting broader adoption of online adaptive strategies in esophageal radiotherapy.