2335 - Outcomes and Prognostic Factors after Metastasis Directed Radiation in Patients with Metastatic Sarcoma
Presenter(s)
J. Joshi1, H. Dorsey1, R. Evans2, S. R. Alcorn1, S. A. Terezakis1, and L. Chang3; 1Department of Radiation Oncology, University of Minnesota School of Medicine, Minneapolis, MN, 2Clinical and Translational Science Institute, University of Minnesota, Minneapolis, MN, 3Department of Radiation Oncology, University of Minnesota Medical School, Minneapolis, MN
Purpose/Objective(s): We evaluated local control and overall survival (OS) following metastasis directed radiation in patients with metastatic sarcoma to identify clinical and treatment-related predictors for local failure and mortality.
Materials/Methods: We conducted a retrospective review of patients with metastatic bone or soft tissue sarcoma treated with radiation. Local control was analyzed using clustered Cox proportional hazard model to account for multiple metastases treated per patient. OS was assessed using multivariable Cox regression with backward selection to identify independent predictors of mortality.
Results: We identified 92 patients with a total of 175 metastatic lesions treated with metastatic site radiation. Median age at diagnosis was 52 years (range: 5-91), median follow up after radiation was 9.1 months (range: 0.2-127). The most common histologies were Ewing’s sarcoma (16%) and leiomyosarcoma (16%). At the time of radiation, metastatic burden was balanced across the cohort, with half of patients (50%) presenting with one or two metastases and the remainder with three or more. The median interval between metastatic site diagnosis and radiation shortened with each additional site treated, decreasing from 112 days for the first site to 18 days for the sixth. Most metastatic sites (96%) were treated with palliative doses with median EQD2 (a/b=3) of 40Gy (range: 9.7-130). Local failure across all treated metastatic sites was 12.5%. Univariable analysis demonstrated early diagnosis of a metastatic site was associated with improved local control, (Hazard Ratio (HR) 0.91 per additional month, 95% Confidence Interval (CI) 0.84–0.98; p=0.01). Prior radiation at the treatment site was associated with increased risk of local failure (HR: 2.36, 95% CI: 1.14-4.86, p=0.02). Location of metastatic site, BED3, EQD2, and PTV volume, were not associated with local control. On multivariate analysis, higher Karnofsky Performance Status was associated with improved OS (HR: 0.97, 95% CI: 0.96-0.99, p<0.01). Male sex (HR: 2.28, 95% CI: 1.27-4.08 p<0.01) and patients with multiple metastases at time of radiation had a significantly higher risk of death, including 2 metastases (HR 3.91), 3–5 metastases (HR 2.12), and >5 metastases (HR 3.07), all p<0.05. The model-adjusted median overall survival was 35.6 months (interquartile range, 12.6–124.2).
Conclusion: Metastatic site radiation achieved durable local control in patients with metastatic sarcoma, with prior radiation at the treatment site emerging as the strongest predictor of local failure. Local failure in previously irradiated sites highlights a higher risk subgroup which may benefit from alternative local control strategies. Survival outcomes were associated with performance status and metastatic burden at time of radiation. Early integration of radiation in patients with limited metastatic burden may be critical to optimizing the benefit of local therapy and warrants further prospective evaluation.