Stereotactic Body Radiation Therapy for Sarcoma Pulmonary Metastases: Outcomes and Fractionation Schedules

Abstract

<h3>Purpose/Objective(s)</h3> Lung metastases are the most common site for distant metastases in sarcoma. Mastectomy is associated with improved survival in select patients; however, alternatives such as stereotactic body radiation therapy (SBRT) can be considered for inoperable patients or those who prefer non-surgical management. However, data regarding local control and optimal fractionation are limited. We present outcomes of 3 SBRT regimens, describe patterns of failure and chemotherapy free survival rates after SBRT for sarcoma lung metastases. <h3>Materials/Methods</h3> 50 sarcoma patients were treated with SBRT for 109 lung metastases between 2005 and 2021 with dose regimens including 30-34Gy/1fx (BED₁₀ 120-149.6 Gy), 48Gy-50Gy/4-5fx (BED₁₀ 100-106), and 60Gy/5fx (BED₁₀ 132). At least 6 month follow up was required. Overall survival (OS), local control (LC), chemotherapy free survival, patterns of failure and toxicity were evaluated. <h3>Results</h3> 10 patients received 30-34Gy/1fx, 24 patients received 48-50Gy/4-5fx and 16 patients received 60Gy/5fx. The most common histology for bone sarcomas was osteosarcoma (<i>n</i>=10), and for soft tissue sarcoma was leiomyosarcoma(<i>n</i>=9). At SBRT, median age was 64 years old and 76% of patients had a KPS ≥80. Median tumor size was 1.9 cm (range: 0.3-6.3). With a median follow-up time from SBRT of 19.5 months, 1- and 3-year LC rates were 96% and 88%, with 1- and 3-year OS of 77% and 50%, respectively. There was no statistically significant difference between the 3 regimens in terms of LC, OS or toxicity. No differences in LC or OS were noted based on primary histology; however, a size 4 cm or larger was predictor of worse LC (p=0.031) and worse OS (p= 0.039) on univariate analysis. The primary pattern of failure was new distant metastases occurring in (64%) of patients of which the majority were in the contralateral lung (52%); 4% had lobar failure, 4% had local only failure, and 4% had both local and distant failure. 1-year chemotherapy free survival was 85%. Overall, 76% of patients did not require chemotherapy initiation or change of chemotherapy regimen after lung SBRT (3 remained on same chemotherapy while receiving SBRT). Toxicity was reported in 16% of patients overall, including 25%, 20% and 14 % in the 30-34Gy/1fx, 48-50Gy/4-5fx and 60Gy/5fx cohorts, respectively. Chest wall toxicity was reported in 5 patients overall (1 patient with Grade II in 30-34Gy/1fx cohort, 3 patients, 1 Grade I, II and III in 48-50Gy/4-5fx cohort, and 1 Grade I in 60Gy/5fx cohort), pneumonitis in 3 patients (1 patient with Grade I in 30-34Gy/1fx cohort, 1 patient with Grade II in 48-50Gy/4-5fx cohort, and 1 patient with Grade II in the 60Gy/5fx cohort). <h3>Conclusion</h3> This series of SBRT for sarcoma pulmonary metastases demonstrates that SBRT is effective with comparable outcomes between dose/fractionation regimens. In addition, lung SBRT is associated with an excellent chemotherapy free survival, and can be a potential alternative to surgical resection.