Stereotactic Ablative Radiation Therapy for Sarcoma Lung Metastases: Indications for Treatment and Patterns of Failure

Abstract

<h3>Purpose/Objective(s)</h3> The lungs are the most common site of metastasis for patients with soft tissue sarcoma. Stereotactic ablative radiation therapy (SABR) is employed to treat lung metastases in select sarcoma patients with limited disease. We sought to evaluate outcomes and patterns of failure among sarcoma patients treated definitively with SABR for their lung metastases. <h3>Materials/Methods</h3> We performed a retrospective review of patients treated at a tertiary cancer center between 2006-2021. The indications for SABR were categorized as either oligorecurrent – meaning the primary disease had been treated and the patient recurred while off of any systemic therapy – or oligoprogressive – defined as a controlled primary lesion but with progressive lung metastases while actively receiving systemic therapy. The Kaplan-Meier method was used estimate actuarial local control (LC), progression-free survival (PFS), and overall survival (OS). Multivariable analyses were conducted using Cox proportional hazards model. <h3>Results</h3> We identified 71 patients treated with SABR to a total of 101 metastatic lesions. The median age was 62 years (range 18-93), and the median follow-up for all patients was 32 months. The most common indication for SABR treatment was treatment of oligorecurrent disease (n=60, 59%) and oligoprogression (n=40, 40%). The most common SABR dose/fractionation schemes used were 50 Gy in 4 fractions (n=70, 69%), followed by 70 Gy in 10 fractions (n=26, 25%). The actuarial 5-yr LC, PFS, and OS for all patients in our cohort was 94%, 21%, and 33%. On univariable analysis, patients with oligoprogressive disease had worse PFS than those with oligorecurrent disease (HR 1.73 [1.103-2.713], p=0.02), and OS (HR 2.58 [1.42-4.71], p=0.002). Patients with systemic disease controlled at the time of SABR had improved PFS (HR 0.48 [0.28 - 0.80], p=0.005) and OS (HR 0.20 [0.10-0.38], p<0.001). Receipt of comprehensive SABR to all sites of pulmonary metastatic disease at the time of treatment versus not treating all lesions was also associated with improved PFS (HR 0.57 [0.362 - 0.901], p=0.02) but not OS. On multivariable analysis, only having systemic disease controlled at the time of SABR, which we defined as no progressive disease detected on imaging within 3 months of treatment, predicted for improved PFS (HR 0.54, [0.31-0.92], p=0.02) and OS (0.20 [0.10-0.40], p<0.001). SABR treatment was well tolerated with no patients having grade 3 or higher pulmonary, esophageal, cardiac, or chest wall toxicities. <h3>Conclusion</h3> SABR provides durable long-term LC for sarcoma lung metastases. Patients presenting with oligorecurrent disease have improved PFS and OS relative to those treated due to oligoprogression. The most important predictor for improved outcomes was whether or not systemic disease was effectively controlled at the time of treatment. Careful consideration of these factors should help guide decisions in a multidisciplinary setting to appropriately select the optimal candidates for SABR.