# Lung Stereotactic Body Radiotherapy (SBRT) on Metastatic Sarcomas: A Retrospective Study at a Quaternary Center

## TL;DR

This study shows that SBRT is effective for treating lung metastases in sarcoma patients, with good local control and minimal side effects.

## Contribution

The study provides new evidence on the effectiveness of SBRT for sarcoma lung metastases with long-term follow-up data.

## Key findings

- SBRT achieved 3-year local failure rate of 47.2% with no reported toxicities.
- Median systemic therapy-free survival was 26 months, and median overall survival was 34 months.
- Most treatment courses targeted the only active site of disease, with high biologically effective doses.

## Abstract

Introduction and purpose: Lung metastases are common in sarcoma patients, often necessitating systemic therapy or local therapies. Stereotactic body radiotherapy (SBRT) offers a targeted approach, achieving low local failure (LF) and delaying systemic therapy. This study evaluates the outcomes of SBRT for sarcoma lung metastases, focusing on LF, systemic therapy-free survival (STFS), and overall survival (OS).

Methods and materials: Retrospective study of patients with metastatic pulmonary lesions treated with SBRT between September 2015 and December 2022. STFS was defined as the time from the end of the first RT course to the start of any systemic therapy, if no previous systemic therapy was given or if a pause of at least one month was achieved with RT. STFS was depicted as a Kaplan-Meier curve. LF was analyzed using a competing risks framework. The response assessment was evaluated based on pre- and post-treatment chest CT or PET-CT. Toxicities were classified according to the Common Terminology Criteria for Adverse Events (CTCAE), version 5.0.

Results: A total of 17 patients and 53 lesions were treated in 31 courses of treatment. Median follow-up was 96 months. Median number of lesions treated per treatment course was 2 (range: 1-4). In 94.1% of the treatment courses, the target was the only active site of active disease. In 79.2% of the lesions treated, the biologically effective dose (BED) was equal to or superior to 100Gy with a median BED of treated lesions of 105.6Gy (range: 67.2-180Gy). No SBRT-related toxicities were reported. LF rates at one-, two-, and three-years were 32.0%, 45.3% and 47.2%, respectively. Median STFS was 26 months. STFS rates at one- and two-years were 62% (CI95% 40-95) and 54% (CI95% 33-89), respectively. Median OS was 34 months. OS rates at one- and two-years were both 71% (CI95% 53.3-85.6).

Conclusion: SBRT is a promising strategy for managing lung metastases in sarcoma, offering acceptable local control (LC) rates and significant systemic therapy-free survival without accrued toxicities. Further research should focus on optimizing dose schedules and patient selection to enhance outcomes.