Balancing tumor control and toxicity: SBRT strategies for ultra-central NSCLC.

e20018 Background: Stereotactic body radiation therapy (SBRT) has shown exceptional efficacy for early-stage non-small cell lung cancer (NSCLC). However, treating ultra-central NSCLC (UCNLC)-tumors located near critical organs at risk (OARs)-remains a challenge due to potential toxicities. Advances in personalized radiotherapy planning may enable safe and effective treatment for these patients. This study evaluates the efficacy and safety of tailored SBRT approaches for UCNLC. Methods: This retrospective study analyzed 66 patients with stage I-II unresectable UCNLC treated with SBRT at Shanghai Pulmonary Hospital from January 2020 to December 2023. UCNLC was defined as tumors with planning target volume (PTV) abutting or overlapping the proximal bronchial tree (PBT), esophagus, heart, great vessels, or pulmonary vessels, or within 1 cm of these structures. Individualized SBRT plans, incorporating non-uniform PTV compromises, were developed to meet stringent OAR constraints. 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 treatment-related toxicity. Results: The OAR constraints in this study included both maximum dose and volumetric thresholds to ensure comprehensive protection of critical structures. To facilitate safe dose delivery under these stringent constraints, non-uniform PTV compromises were applied in 45.5% of patients, allowing 53.3% to achieve a BED 10 of 100 Gy. After a median follow-up of 23.7 months, 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. LC rates were 98.5% at 1 year and 81.4% at 3 years, while OS rates were 98.5% at 1 year and 92.8% at 3 years. Toxicity was minimal, with acute toxicities including grade 1 radiation pneumonitis in 28.8% of patients, grade 2 in 7.6%, and only one instance of grade 3 pneumonitis (1.5%). Long-term toxicities were also mild, with 9% experiencing grade 1 pulmonary fibrosis and one case of grade 2 fibrosis. No severe toxicities (> grade 3) were observed under the strict OAR constraints. Importantly, non-uniform PTV compromises did not adversely affect survival outcomes, highlighting their value in safely delivering effective SBRT for UCLC. Conclusions: Tailored SBRT, utilizing non-uniform PTV compromises and stringent OAR constraints, demonstrated excellent tumor control and minimal toxicity in UCNLC patients. These personalized treatment plans effectively managed ultra-central tumors, even in the most challenging cases. These results highlight the feasibility and effectiveness of individualized radiotherapy approaches, reinforcing SBRT as a safe and viable treatment option for UCLC.