2519 - Refining SBRT for Ultra-Central NSCLC: Non-Uniform PTV and Strict OAR Constraints for Optimal Control and Minimal Toxicity
Presenter(s)
D. Liu1, S. Yang1, Y. Chen1, M. Liu2, R. Zhao1, M. Hu1, B. Su1, Q. Wu1, H. Wu1, H. Liu1, and Y. Xu1; 1Department of Radiation Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China, 2Department of Radiation Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, SHANGHAI, China
Purpose/Objective(s): Ultra-central non-small cell lung cancer (UCNLC) poses significant therapeutic challenges due to close proximity to critical organs at risk (OARs). This study aimed to assess the feasibility, safety, and efficacy of a tailored stereotactic body radiation therapy (SBRT) approach employing non-uniform planning target volume (PTV) strategies and stringent OAR constraints in patients with UCNLC.
Materials/Methods: We retrospectively analyzed 66 patients with early-stage, unresectable UCNLC treated at Shanghai Pulmonary Hospital between January 2020 and December 2023. UCNLC was defined as tumors with the PTV abutting or overlapping major structures (e.g., proximal bronchial tree, esophagus, heart, great vessels) or within 1 cm of these organs. When the PTV abutted OARs, the target volume was trimmed (PTV_crop) to meet strict OAR constraints. If the PTV overlapped OARs, it was divided into PTV_high and PTV_low sub-volumes to optimize dose distribution while respecting OAR limits. Prescribed doses covered =95% of the relevant PTV volumes at the prescription isodose line, ensuring 99% of each sub-volume received =90% of the prescribed dose, with PTV_low receiving =80% coverage. Toxicities were graded according to standard criteria. The primary endpoints were local control (LC) and progression-free survival (PFS), while secondary endpoints included regional control (RC), distant control (DC), overall survival (OS), and toxicity.
Results: Non-uniform PTV compromises were employed in 45.5% of patients, allowing 53.3% to achieve a biologically effective dose of 100 Gy. After a median follow-up of 23.7 months. The median LC was not reached, with LC rates 98.5% at 1 year and 81.4% at 3 years. The median PFS was 42.9 months (95% CI: 34.5–51.3), with 1- and 3-year PFS rates of 93.9% and 67.0%, respectively. The median OS was not reached, with the 1- and 3-year OS rates of 98.5% and 92.8%, respectively. Toxicities were predominantly mild (grade 1–2), with only one patient experiencing grade 3 pneumonitis. Larger ITV was associated with poorer LC and PFS, and Cox regression identified T stage as an independent predictor of PFS. Notably, non-uniform PTV compromises did not adversely affect survival outcomes.
Conclusion: Tailored SBRT, employing non-uniform PTV modifications and stringent OAR constraints, achieved excellent tumor control with minimal toxicity in UCNLC patients. These personalized treatment plans effectively managed the most challenging cases, reinforcing SBRT as a safe and viable option for UCNLC.