# Real-World Data on the Safety and Efficacy of SBRT for Central and Ultra-Central Lung Tumors: A Retrospective Multi-Center Cohort

## TL;DR

This study shows that stereotactic body radiotherapy (SBRT) is safe and effective for treating central and ultra-central lung tumors when delivered with careful planning.

## Contribution

The study provides real-world evidence that SBRT can be safely used for central and ultra-central lung tumors with minimal toxicity.

## Key findings

- SBRT achieved excellent local tumor control with very low rates of clinically relevant side effects.
- No severe or treatment-related deaths were observed in the cohort.
- Four-year local progression-free survival was 97.4% for the entire cohort.

## Abstract

Stereotactic body radiotherapy (SBRT) is an effective treatment for patients with early-stage lung cancer who are not suitable for surgery. However, when lung tumors are located close to critical structures such as the airways, heart, or major blood vessels (so-called central and ultra-central tumors), treatment is more challenging and safety concerns remain. In this study, we evaluated the real-world outcomes of SBRT in patients with centrally and ultra-centrally located early-stage non–small cell lung cancer treated according to established planning principles. We found that SBRT achieved excellent local tumor control with very low rates of clinically relevant side effects, even for ultra-central tumors. Importantly, no severe or treatment-related deaths were observed. These findings suggest that, when careful treatment planning and strict protection of nearby organs are applied, SBRT can be safely used for selected patients with central and ultra-central lung tumors in routine clinical practice.

Background/Objectives: The use of stereotactic body radiotherapy (SBRT) for centrally and ultra-centrally located early-stage non-small cell lung cancer (NSCLC) remains clinically challenging due to the proximity of critical mediastinal organs at risk and the limited prospective evidence, particularly for ultra-central disease. Real-world data are needed to better define the safety and efficacy of SBRT when delivered according to contemporary protocol-based planning principles. Methods: This retrospective cohort study included patients treated at two radiotherapy centers, with centralized follow-up and outcome adjudication at a single academic institution. We evaluated patients with centrally or ultra-centrally located, early-stage NSCLC treated with SBRT according to dose-fractionation and planning principles derived from the NRG Oncology/RTOG 0813 protocol. Tumors were classified as central or ultra-central according to the International Association for the Study of Lung Cancer and HILUS definitions, respectively. The prescribed dose was 50 Gy in five fractions. Primary endpoints were treatment-related toxicity and local progression-free survival (LPFS). Secondary endpoints included overall survival (OS), progression-free survival (PFS), and dosimetric outcomes. Survival endpoints were analyzed using the Kaplan–Meier method. Results: Seventy-eight patients were included, of whom 52 had centrally located and 26 ultra-centrally located tumors. Median follow-up was 57 months. The overall objective response rate was 92.3%. The estimated 4-year LPFS was 97.4% for the entire cohort, with rates of 100% for central and 91.6% for ultra-central tumors (p < 0.001). Four-year OS was 98.7%, with no treatment-related deaths observed. Treatment-related toxicity was minimal, with grade ≥ 2 events occurring in only one patient (1.3%) and no grade ≥ 3 toxicity. All treatment plans met predefined organ-at-risk dose constraints. Conclusions: In this real-world cohort, SBRT delivered according to RTOG 0813 planning principles achieved excellent local control with minimal clinically relevant toxicity in patients with centrally and ultra-centrally located early-stage NSCLC. These findings support the safe implementation of SBRT in carefully selected patients when stringent organ-at-risk constraints and conservative treatment planning are employed.