Abstract
BACKGROUND: Stereotactic body radiotherapy (SBRT) is increasingly used to treat oligometastatic disease (OMD), but the effect of metastasis timing on patient outcomes remains uncertain. METHODS: An international database of patients with OMD treated with SBRT was assembled with rigorous quality assurance. Early versus late metastases were defined as those diagnosed ≤24 versus >24 months from the primary tumor. Overall survival (OS), progression-free survival (PFS), and incidences of wide-spread progression (WSP) were estimated using multivariable Cox proportional hazard models stratified by primary tumor types. RESULTS: The database consists of 1033 patients with median follow-up of 24.1 months (0.3-104.7). Late metastatic presentation (N = 427) was associated with improved OS compared to early metastasis (median survival 53.6 vs. 33.0 months, hazard ratio [HR] 0.59, 95% confidence interval [CI]: 0.47-0.72, p < 0.0001). Patients with non-small cell lung cancer (NSCLC, N = 255, HR 0.49, 95% CI: 0.33-0.74, p = 0.0005) and colorectal cancer (N = 235, HR 0.50, 95% CI: 0.30-0.84, p = 0.008) had better OS if presenting with late metastasis. Late metastasis correlated with longer PFS (median 17.1 vs. 9.0 months, HR 0.71, 95% CI: 0.61-0.83, p < 0.0001) and lower 2-year incidence of WSP (26.1% vs. 43.6%, HR 0.60, 95% CI: 0.49-0.74, p < 0.0001). Fewer WSP were observed in patients with NSCLC (HR 0.52, 95% CI: 0.33-0.83, p = 0.006) and kidney cancer (N = 63, HR 0.37, 95% CI: 0.14-0.97, p = 0.044) with late metastases. Across cancer types, greater SBRT target size was a significant predictor for worse OS. CONCLUSION: Late metastatic presentation is associated with improved survival and delayed progression in patients with OMD treated with SBRT.