In a registry-based observational study reported in The Lancet Oncology, Anastasia Chalkidou, PhD, and colleagues found that stereotactic ablative body radiotherapy (SABR) was associated with high overall survival and low rates of toxicity in patients with extracranial oligometastatic cancers.
The prospective observational study involved data from 1,422 patients from a registry created by the National Health Service (NHS) England to evaluate SABR in oligometastatic cancers. Patients were enrolled between June 2015 and January 2019 from 17 NHS radiotherapy centers. Eligibility requirements were age 18 years or older; confirmed primary solid cancer; one to three extracranial metastatic lesions; a disease-free interval from primary tumor development to metastases of longer than 6 months (with the exception of synchronous colorectal liver metastases); World Health Organization performance status of 2 or lower; and life expectancy of 6 months or longer.
The primary outcome measure was overall survival at 1 year and 2 years from the start of SABR treatment. The study has been completed.
Patients had a median age of 69 years, 67% were male, and the most common primary tumors among patients were prostate (28.6%), colorectal (27.9%), and renal cancers (10.1%). The number of metastases was one in 75.6% of patients, two in 19.6%, and three in 4.8%. SBRT doses ranged from 24 to 60 Gy administered in three (55.9%) to eight (10.9%) fractions. Median follow-up was 13 months.
Overall survival was 92.3% (95% confidence interval [CI] = 90.5%–93.9%) at 1 year and 79.2% (95% CI = 76.0%–82.1%) at 2 years. According to primary tumor type, 2-year overall survival was 60.5% for patients with melanoma, 65.4% for lung cancer, 77.8% for rectal cancer, 80.3% for colon cancer, 82.4% for renal cancer, 83.2% for breast cancer, and 94.6% for prostate cancer. Local control rates were 86.9% at 1 year and 72.3% at 2 years. Metastasis-free survival was 84.0% at 1 year and 52.0% at 2 years.
The most common treatment-related adverse events of any grade were fatigue (56.4%) and cough (16.0%), and the most common grade 3 or 4 events were fatigue (2.0%) and increased bilirubin (1.1%). No fatal adverse events were reported.
The investigators concluded, “In patients with extracranial oligometastatic cancer, use of SABR was associated with high overall survival and low toxicity. The study findings complement existing evidence from a randomized phase II trial and represent high-level, real-world evidence supporting the use of SABR in this patient cohort, with a phase III randomized controlled trial to confirm these findings underway. Based on the selection criteria in this study, SABR was commissioned by NHS England in March 2020, as a treatment option for patients with oligo-metastatic disease.”