2904 - Dosimetric Benefits of Adaptive Radiotherapy for Nasopharyngeal Carcinoma: A Weekly FBCT-Based Dose Accumulation Study
Presenter(s)
M. Hao1,2, Y. X. Yang2, G. Q. Zhou2, L. Lin2, L. Jia3, H. Li3, Y. Liu3, W. Zhang4, J. Zhou4, R. Guo2, X. Yu5, X. Yang2, G. Y. Wang2, and Y. Sun6; 1Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China, 2Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangzhou, China, 3Shenzhen United Imaging Research Institute of Innovative Medical Equipment, Shenzhen, China, 4Shanghai United Imaging Healthcare Co., Ltd., Shanghai, China, 5The Second Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China, 6State Key Laboratory of Oncology in South China, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangdong Provincial Clinical Research Center for Cancer, Department of Radiation Oncology, Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China
Purpose/Objective(s): We have successfully established an artificial intelligence-powered online adaptive radiation radiotherapy (ART) workflow for nasopharyngeal carcinoma (NPC) and completed its clinical implementation. This study aimed to quantitatively assess the dosimetric benefits of online ART through weekly FBCT-based dose accumulation analysis.
Materials/Methods: Between April 2022 and November 2023, 120 consecutive patients with newly diagnosed non-metastatic NPC receiving definitive radiotherapy were enrolled at our institution. All participants underwent a single session of online ART (median fraction: 21st, range: 15th–30th), timed based on anatomical variations, weight changes, or toxicity. For all patients, weekly FBCT images were acquired, with the scanning range identical to that of the original planning CT, including the FBCT acquired on the ART treatment day (FBCT_ART). Two cumulative dose scenarios were analyzed: 1) Cumdose_non-ART: Original plans propagated to weekly FBCT to generate the weekly plan (plan_original), then deformable registered to FBCT_ART; 2) Cumdose_ART: the original plan was copied onto weekly FBCT before online ART to generate plan_original, the online ART plan was copied onto the weekly FBCT after online ART to generate plan_ART, Both plan_original and plan_ART were deformable registered to FBCT_ART. Dosimetric parameters for targets and OARs were compared using paired tests (significance: p<0.001).
Results: The analysis showed significantly better PTV coverage and improved control of PTV hotspots with online ART compared to non-ART. Specifically, the V100% for PGTVn and PCTV2 with non-ART were 85.4%±11.2% and 93.9%±3.2% respectively, while with ART they improved to 87.9%±12.5% and 94.8%±2.9% (p<0.001). Hotspot reductions were observed: PGTVn V107% decreased from 12.2%±16.3% (non-ART) to 6.6%±12.4% (ART), and PCTV2 V110% declined from 50.4%±8.4% (non-ART) to 48.5%±7.9% (ART) (p<0.001). Compared to non-ART, ART achieved superior OAR sparing, with D0.03cc for spinal cord (3262.7±232.5 vs. 3366.1±255.7 cGy), brainstem (5418.8±526.4 vs. 5492.9±541.0 cGy), temporal lobes (6895.2±433.0 vs. 6919.6±433.1 cGy), optic chiasm (2769.3±1630.2 vs. 2860.1±1645.4 cGy), optic nerves (2844.4±1591.1 vs. 2917.3±1606.9 cGy), and mandibles (6419.2±547.7 vs. 6487.1±564.4 cGy) showing statistically significant improvements (p<0.001). Dose reductions were also observed in eyes, lenses, parotid glands, oral cavity, and thyroid.
Conclusion: Cumulative dose analysis demonstrated that online ART for NPC consistently improved target coverage while enhancing OARs protection compared to non-adaptive approaches. These findings support the clinical integration of AI-driven adaptive strategies to optimize therapeutic precision.