Stereotactic ablative body radiotherapy (SABR/SBRT) for extracranial oligometastatic solid cancers with one to three metastases: a prospective national registry-based single-arm observational evaluation study

Abstract

Background: Stereotactic ablative body radiotherapy (SABR), also termed stereotactic body radiotherapy (SBRT), is increasingly used for metastasis-directed treatment of oligometastatic cancer, but high-level evidence to inform health policy is scarce. Additional real-world evidence is needed. We report results from a national study of patients with extracranial oligometastases treated with SABR, representing, to our knowledge, the largest dataset on outcomes in this population so far. Methods: In 2015, National Health Service (NHS) England launched a Commissioning through Evaluation scheme funding a prospective, registry-based, single-arm, observational evaluation study of SABR for patients with solid cancer and extracranial oligometastatic disease. Prescribed radiotherapy doses were 24–60 Gy delivered in three to eight fractions. The study was conducted at 17 NHS radiotherapy centres in England. Eligible patients were aged 18 years or older with confirmed primary carcinoma, excluding haematological malignancies; one to three extracranial metastatic lesions; a disease-free interval from primary tumour development to metastases longer than 6 months, except for synchronous colorectal liver metastases; WHO performance status 2 or lower; and life expectancy of at least 6 months. The primary endpoint was overall survival at 1 year and 2 years from the start of SABR. The study is completed. Findings: Between June 15, 2015, and Jan 30, 2019, 1422 patients were recruited from 17 hospitals in England. Median age was 69 years (IQR 62–76), and prostate cancer was the most common primary tumour (406 [28.6%] patients). Median follow-up was 13 months (IQR 6–23). Overall survival was 92.3% (95% CI 90.5–93.9) at 1 year and 79.2% (76.0–82.1) at 2 years. The most common grade 3 adverse event was fatigue (28 [2.0%] of 1422 patients), and the most common serious grade 4 event was increased liver enzymes (nine [0.6%]). No treatment-related deaths were reported. Interpretation: In patients with extracranial oligometastatic cancer, SABR was associated with high overall survival and low toxicity. These findings complement evidence from a randomised phase 2 trial and provide high-level real-world evidence supporting SABR in this patient cohort, with a phase 3 randomised controlled trial underway to confirm the findings. On the basis of the selection criteria in this study, NHS England commissioned SABR in March, 2020, as a treatment option for patients with oligometastatic disease. Funding: NHS England Commissioning through Evaluation scheme.