Definitive carbon ion radiotherapy for thoracic bone and soft tissue sarcoma

Thoracic bone and soft tissue sarcoma (BSTS) represents a rare malignancy. For patients with medically inoperable BSTS, radiotherapy (RT) is a recommended treatment modality. Carbon ion radiotherapy (CIRT) has shown superior efficacy compared to photon-based RT. However, data on the use of CIRT for thoracic BSTS remain scarce. This study aimed to evaluate the clinical outcomes and toxicity profile of CIRT in patients with thoracic BSTS.

The inclusion criteria were as follows: 1) ≥ 14 years old; 2) primary or metastatic BSTS in chest area, with histologically confirmed primary tumor; 3) with visible lesion; 4) definitive CIRT intent; and 5) had at least one follow-up, and the time between follow-up and the first fraction of CIRT was longer than 1 month. The prescribed CIRT doses ranged from 59.5 to 80 Gy (RBE) delivered in 10-23 fractions. Treatment-related toxicities were assessed using the Common Terminology Criteria for Adverse Events Version 4.03, while tumor response was evaluated according to the Response Evaluation Criteria in Solid Tumors Version 1.1. Local control (LC), progression-free survival (PFS), and overall survival (OS) rates were estimated using the Kaplan-Meier method. Subgroup analyses were performed using the Log-rank test.

A total of 33 patients with 35 lesions were included in the study. The median age of the cohort was 56 years (range: 22-86 years), with a median follow-up duration of 42.1 months (range: 3.8-100.6 months). The 3-year LC rates for the entire cohort were 85.2%. There was no statistically significant difference in LC when categorized by median tumor volume and biological effective dose. The use of simultaneous integrated boost technology appears to improve the LC. Among patients with primary thoracic BSTS, the 3-year LC, PFS， and OS rates were 84%, 54.8%， and 76.7%, respectively. Patients with postoperative recurrence (PORC) demonstrated significantly inferior PFS and OS. Except one case of grade 3 chest wall pain and 1 brachial plexopathy, no grade ≥ 3 toxicities were observed.

CIRT is safe and effective in the management of thoracic BSTS. Further studies with more cases and longer observation periods are warranted.

Retrospectively registered on 13th February, 2026; ChiCTR2600118943; Chinese Clinical Trial Registry; https://www.chictr.org.cn/bin/project/edit?pid=308155.