Clinical outcomes of stereotactic body radiotherapy in oligometastatic disease: a national real-world cohort study

Purpose We conducted the first multicentre Spanish real-world study assessing the efficacy and safety of stereotactic body radiotherapy (SBRT) in oligometastatic patients treated in routine clinical practice. Methods This retrospective, multicentre observational study included oligometastatic patients with primary solid tumours treated with SBRT between 2020 and 2024 across 12 Spanish radiotherapy centres. The primary endpoint was 1-year progression-free survival (PFS). The secondary endpoints included overall survival (OS), local control (LC), and acute and late adverse events by CTCAE v.5.0. Results 300 patients with 451 treated lesions were included. Median age was 69 years. After a median follow-up of 22 months, 1- and 2-year PFS were 45.1% and 36.3% respectively, with a median PFS of 11 months (95% CI, 9–13). The 1- and 2-year OS were 92% and 82.9% (median not reached), and 1- and 2-year LC were 90.5% and 85.5% respectively. Multivariable analyses showed significantly better PFS and OS in prostate cancer patients. Repeat and induced oligometastatic patients showed worse PFS than those with synchronous disease (HR 2.86, 95% CI 1.59–5.13; p <0.001 and HR 2.97, 95% CI 1.58–5.57; p <0.001, respectively). Visceral-only disease also correlated with worse PFS compared to bone-only metastases. Local control was poorer in lesions ≥5 cm compared to <5 cm ( p <0.001). Grade ≥3 acute and late adverse events occurred in 0.7% and 1% of patients. Conclusion In this real-world multicentre cohort, SBRT to the oligometastases showed efficacy with minimal adverse events. Prognostic differences among subgroups underscore the importance of an adequate patient selection and individualized treatment strategies.