3443 - 4DCT Ventilation Imaging-Guided Functional Lung Avoidance Radiotherapy: A Dosimetric and NTCP-Predicted Radiation Pneumonitis Risk Assessment
Presenter(s)
Z. Chen1,2, C. Tan2, P. Shi3, Z. Xiu1, J. Yuan1, D. Tang1, F. Chen1, M. Fan4, Q. Wang5, P. Xue3, Z. Yang2, and Z. G. Guo2; 1West China Longquan Hospital, Sichuan University; The First People’s Hospital of Longquanyi District, Chengdu, SiChuan, China, 2The Second Affiliated Hospital of Chongqing Medical University, Chongqing, Chongqing, China, 3Low-Altitude Science and Engineering College, Shandong University, Weihai, Shandong, China, 4Sichuan Cancer Hospital and Research Institute, University of Electronic Science and Technology of China, Chengdu, China, 5Sichuan Cancer hospital institute/Sichuan Cancer Center/School of Medicine,University of Electronic Science and Technology of China, chengdu, China
Purpose/Objective(s): The hypothesis is that 4DCT ventilation imaging–guided functional lung avoidance radiotherapy (FLAR) reduces dose to highly functional lung and lowers the predicted risk of grade =2 radiation pneumonitis (RP) compared with conventional planning. The primary objective was to quantify functional lung dose reduction and QUANTEC NTCP–predicted RP risk.
Materials/Methods: A retrospective paired dosimetric analysis was conducted in 180 patients undergoing thoracic radiotherapy with 4DCT simulation. Ventilation maps were generated from 4DCT, and high-function lung regions were defined using relative ventilation thresholds (FL70, FL80, FL90), with ipsilateral FL90 prioritized. Conventional and FLAR plans were generated with identical target coverage and prescription doses of 45–66 Gy. Dosimetric parameters were compared using paired t-tests or Wilcoxon tests. RP was assessed radiographically at 3, 6, and 12 months. The QUANTEC NTCP model estimated predicted grade =2 RP risk. An independent prospective 4DCT cohort (n=30) was used for external model assessment based on paired replanning.
Results: FLAR significantly reduced dose to highly functional lung (FL90). Mean iFL90-V10 decreased from 34.52% to 29.16% (absolute difference -5.36%, 15.5% relative reduction), iFL90-V20 from 25.51% to 21.50% (absolute difference -4.01%, 15.7% relative reduction), iFL90-V30 from 19.98% to 17.13% (absolute difference -2.85%, 14.3% relative reduction), and iFL90 mean lung dose from 13.24 Gy to 11.68 Gy (absolute difference -1.56 Gy, 11.8% relative reduction) (all P < 0.001). Dose reductions followed FL90 > FL80 > FL70, with comparable target coverage and organ-at-risk doses. Grade =2 RP increased across tertiles of baseline iFL90 mean lung dose (3.2%, 22.2%, 31.1%). iFL90 mean lung dose showed better NTCP discrimination than conventional mean lung dose (AUC 0.705 vs 0.572). In the prospective cohort, NTCP-predicted grade =2 RP was lower with FLAR than conventional replanning (27.00% vs 14.60%), with an absolute predicted risk difference of 12.39%.
Conclusion: 4DCT ventilation imaging–guided functional lung avoidance radiotherapy reduces dose to highly functional lung and is associated with a meaningful reduction in QUANTEC model–predicted grade =2 radiation pneumonitis risk without compromising target coverage, supporting integration of functional lung information into thoracic radiotherapy planning.