Stereotactic body radiotherapy for pulmonary oligometastases: a monoinstitutional analysis of clinical outcomes and potential prognostic factors

Purpose: We report the retrospective data of a cohort of patients who received stereotactic body radiotherapy for pulmonary oligometastases, aiming to assess the clinical factors potentially affecting clinical outcomes.

Methods: The present series reports the outcomes of a cohort of 71 patients with pulmonary oligometastases with no extrapulmonary disease. All patients were treated with stereotactic body radiotherapy (SBRT) performed with volumetric modulated arc therapy-image guided radiotherapy (VMAT-IGRT) to up to five secondary lesions. Survival estimates were performed using the Kaplan-Meier method.

Results: A total of 98 lesions in 71 patients were treated from February 2014 to August 2020. The most frequent histologies were colorectal in 37.7%, lung cancer in 44.8%, head and neck cancer in 8.1%, and other in 9.4%. Median age was 71 years (range 32-93 years). Concurrent systemic therapy was administered in 32.3%. SBRT was delivered to a median total dose of 60 Gy (range 55-70 Gy) in 3-10 fractions for a median BED₁₀ = 105 Gy (range 96-180 Gy). Median follow-up was 29.5 months (range 6-81), with no acute or late G > 2 adverse event. Our LC rates at 2 and 4 years were 92.4 and 89.8%, respectively. DPFS rates at 2 and 4 years were 45.3 and 27.2%, respectively. A second SBRT course was proposed in 21 patients (29.5%) who developed an oligoprogression, resulting in median time to second progression of 9 months (range 2-44) and 2‑year PFS2 rate of 42.4%. At univariate analysis, patients with sequential oligometastases reported better OS rates (p = 0.002), which was also confirmed at multivariate analysis, where distant progression was also related to worse OS (p = 0.022). Higher local control rates relate to better PFS (p = 0.04). The 2‑ and 4‑year OS rates were 61 and 39.7% CONCLUSION: SBRT is feasible for pulmonary oligometastases with favorable outcomes and toxicity. At multivariate analysis, patients with sequential oligometastatic progression maintain a survival advantage. Also, local control was found to be related to improved PFS rates.