Safety, efficacy and patterns of failure after single fraction stereotactic body radiotherapy (SBRT) for oligometastases

Sogono, Paolo; Bressel, Mathias; David, Steven; Shaw, Mark; Chander, Sarat; Chu, Julie; Plumridge, Nikki; Byrne, Keelan; Hardcastle, Nick; Kron, Tomas; Wheeler, Greg; Hanna, Gerard G.; MacManus, Michael; Ball, David; Siva, Shankar

Purpose Fewer attendances for radiotherapy results in increased efficiency and less foot traffic within a radiotherapy department. We investigated outcomes after single fraction (SF) SBRT in patients with oligometastatic disease. Methods and Materials Between February 2010 and June 2019, patients who received SF SBRT to 1-5 sites of oligometastatic disease were included in this retrospective study. The primary objective was to describe patterns of first failure after SBRT. Secondary objectives included overall survival (OS) progression-free survival (PFS), high-grade treatment-related toxicity (≥grade 3 CTCAE) and freedom from systemic therapy (FFST). Results In total, 371 patients with 494 extracranial oligometastases received SF SBRT ranging from 16Gy to 28Gy. The most common primary malignancies were prostate (n=107), lung (n=63), kidney (n=52), gastrointestinal (n=51), and breast cancers (n = 42). The median follow-up was 3.1 years. The 1, 3 and 5 year OS was 93%, 69% and 55%, respectively, PFS was 48%, 19% and 14%, respectively, and FFST was 70%, 43% and 35%, respectively. Twelve patients (3%) developed grade 3-4 treatment-related toxicity, with no grade 5 toxicity. As the first site of failure, the cumulative incidence of local failure (irrespective of other failures) at 1, 3 and 5-years was 4%, 8% and 8%, locoregional relapse at the primary was 10%, 18% and 18%, and distant failure was 45%, 66% and 70%, respectively. Conclusions SF SBRT is safe, effective, and a significant proportion of patients remain FFST for several years after therapy. This approach could be considered in resource constrained or bundled payment environments. Locoregional failure of the primary site is the second most common pattern of failure, suggesting a role for optimization of primary control during metastasis-directed therapy.