Stereotactic body radiotherapy for oligometastatic soft tissue sarcoma

Background: Stereotactic body radiotherapy (SBRT) is emerging as a novel treatment option in metastatic soft tissue sarcoma (STS). The aim of our study was to evaluate the effectiveness of exclusive SBRT on disease control and survival in oligometastatic (≤ 3 synchronous lesions) STS.

Materials and methods: In total, 16 consecutive patients, accounting for 26 metastases (including 21 lung and 5 lymph node or soft tissue metastases), were treated at our institution with SBRT. Patient- and treatment-related characteristics were collected. Local control (LC), overall survival (OS), distant metastases-free survival (DMFS), and time to initiation of chemotherapy or best supportive care (corrected disease-free survival, cDFS) were assessed.

Results: Four-year OS was 54% and median OS was 69 months [95% confidence interval (CI) 20-118 months]. LC of 26 lesions at 4 years was 78%. Median DMFS and cDFS were 17 (95% CI 5-30 months) and 28 months (95% CI 5-52 months), respectively. Disease-free interval < 24 months from primary tumor treatment to first metastasis was the only predictor of reduced LC, cDFS, and OS (p = 0.022, 0.023, and 0.028, respectively). No acute or chronic grade ≥ 3 toxicity was observed. Median follow-up was 36 months (IQR 18-71 months).

Conclusions: In patients with oligometastatic STS, SBRT yields satisfying local control with minimal toxicity. Median OS was 69 months. Repeated SBRT may be considered to extend disease-free and systemic therapy-free interval. Increased time from primary tumor to first metastasis identifies patients with potentially greater benefit from SBRT.