Predicting Long‑term Survival Following Involved Site Radiotherapy for Oligometastases

The majority of cancer-associated mortalities are due to distant metastases, and systemic therapy alone is generally not curative. Patients with oligometastases are amenable to involved site radiotherapy with the possibility of long-term disease-free survival; however, prognostic factors remain poorly defined. The present retrospective, single institution study consisted of consecutive adult patients with oligometastases from solid tumor malignancy referred to a single high volume radiation oncologist between January 2014 and December 2021. Oligometastases were defined as ≤5 extracranial or intracranial metastatic lesions where all sites of active disease are treatable, including patients requiring treatment of the primary tumor and/or regional lymph nodes. The study population consisted of 130 patients with 207 treated distant metastases. Radical radiotherapy was administered to all areas of known residual disease and included stereotactic radiotherapy (median dose, 27 Gy in 3 fractions) or intensity modulated radiotherapy (median dose, 50 Gy in 15 fractions). At a median follow-up of 28.8 months, the median overall survival was 37.9 months with a 4-year overall survival of 41.1%. The median progression-free survival was 12.3 months and the 4-year progression-free survival was 22.6%. On multivariate an1alysis, the strongest predictors of overall survival were age, ECOG performance status, primary prostate, breast or kidney tumor and pre-radiation serum albumin (P≤0.01 for all). Overall, the present study demonstrated that long-term overall survival was possible after radical treatment for oligometastases and identified potential prognostic factors.