Predictive Factors for Response and Survival in a Cohort of Oligometastatic Patients Treated With Stereotactic Body Radiation Therapy

Purpose This study evaluated patients, treatment, or disease characteristics that could predict response to stereotactic body radiation therapy (SBRT) and survival in a database of patients with oligometastatic disease from different solid tumors. Methods and Materials Patients treated with SBRT for oligometastatic disease between 2014 and 2015 were included. Patients were defined as oligometastatic if they were affected by a maximum of 5 active lesions in 3 different sites. They had to be treated with SBRT with radical intent. Results The study included 358 patients. With a median follow-up of 31.83 months, local control at 6 and 24 months was 94.6% and 78.9%, respectively. Distant progression was recorded in 279 patients (77.9%). Progression-free survival at 6 and 24 months was 66.1% and 18.4%, respectively. At last follow-up, 195 patients (54.5%) were still alive in 59 cases with no evidence of disease. The median overall survival (OS) was 34.7 months (95% confidence interval, 29.66-43.83). OS at 6 and 24 months was 96.07% and 63.57%, respectively. On multivariable analysis, the presence of lung metastases (hazard ratio [HR], 0.50 [0.33-0.75]; P  = .001) and nodal metastases (HR, 0.44 [0.24-0.78]; P  = .005) was related to longer OS. Primary lung cancer (HR, 1.89 [1.14-3.13]; P  = .013), increasing age (HR, 1.02 [1.01-1.04]; P  = .002), and the presence of metastatic sites other than the irradiated ones (HR, 2.19 [1.39-3.43]; P  = .001) were all independent predictors of shorter OS. Local response was associated with OS. Conclusions SBRT for patients with oligometastatic disease is effective. Local response is strongly correlated with patients'’ prognosis, also underlying its relevance in a metastatic setting.