Stereotactic Body Radiation Therapy for Lung Metastases From Sarcoma in Oligometastatic Patients: A Phase 2 Study

Purpose: The lung is the most frequent site of metastasis in patients with sarcoma. Pulmonary metastasectomy is the most common treatment performed. Stereotactic body radiation therapy (SBRT) has proven to be a potential alternative to resection. This prospective phase 2 study aimed to assess the role of SBRT for patients with lung metastases. Methods and materials: Adult patients with up to 4 lung metastases (LMs) ≤5 cm in diameter and unsuitable for surgery were included. Dose prescription was based on site and size: 30 Gy/1 fraction for peripheral lesions ≤10 mm, 60 Gy/3 fractions for peripheral lesions 11 to 20 mm, 48 Gy/4 fractions for peripheral lesions >20 mm, and 60 Gy/8 fractions for central lesions. The primary endpoint was the proportion of treated lesions free from progression at 12 months. Secondary endpoints were disease-free survival (DFS), overall survival (OS), and toxicity. Results: Between March 2015 and December 2020, 44 patients with a total of 71 LMs were enrolled. Twelve-month local control was 98.5% ± 1.4%, reaching the primary aim; the median DFS time was 12 months (95% CI, 8-16 months), and the 1-, 2-, 3-, 4-, and 5-year PFS rates were 50% ± 7.5%, 19.5% ± 6.6%, 11.7% ± 5.8%, 11.7% ± 5.8%, and 11.7% ± 5.8%, respectively. The median OS time was 49 months (95% CI, 24-49 months), and the 1-, 2-, 3-, 4-, and 5-year OS rates were 88.6% ± 4.7%, 66.7 ± 7.6%, 56.8% ± 8.4%, 53.0% ± 8.6%, and 48.2% ± 9.1%, respectively. Prognostic factors recorded as significantly affecting survival were age, grade of primary sarcoma, interval time from diagnosis to occurrence of LMs, and number of LMs. No severe pulmonary toxicity (grade 3-4) occurred. Conclusions: The study found a local control of LMs in almost all patients treated, with negligible toxicity. Survival was also highly satisfactory. Well-designed randomized trials comparing surgery with SBRT for patients with metastatic lung sarcoma are needed to confirm these preliminary data.