BackgroundIn oligoprogressive (OP) cancer there are a limited numbers of metastatic areas progressing on a background of stable or responding widespread cancer. While the standard-of-care for OP is changing systemic therapy (ST), stereotactic body radiotherapy (SBRT) is being explored as an alternative local therapy targeting the sites of progression. Materials/methodsXXX (NCTXXX) was a single-centre phase-2 study of patients with metastatic genitourinary (GU), breast and gastrointestinal (GI) cancers, receiving ST for >3 months, with radiographic OP disease in <5 sites. Patients received SBRT to all OP disease in 1-5 fractions, and were maintained on ST. The primary endpoint was the cumulative incidence of change in ST estimated using Aalen-Johansen method. Secondary endpoints included progression-free survival (PFS) and overall survival (OS) estimated using Kaplan-Meier method, toxicity, and health-related quality-of-life (HRQOL). Comparisons between diagnosis groups were done using log-rank test. A two-sided p-value of <0.05 was considered as statistical significance. ResultsSeventy patients were analyzed, with median age 69 years; 32 patients (46%) were female; median number of lines of prior ST was 3. Primary sites were GU (n=32; 46%), breast (n=23; 33%) and GI (n=15; 21%). Median follow-up was 12.3 months (IQR 8.2-21.6). At 1-year, change in ST occurred in 47% (95% CI 36-61%) (GU 45%, breast 41%, GI 60%, p=0.23). PFS at 1-year was 32% (95% CI 23-45%), and median PFS was 4.7 months (95% CI 3.8-8.1) (GU 4.8, breast 6.5, GI 3.2), which significantly differed by disease type (p=0.006). OS was 75% at 1-year (95% CI 65-87%), which significantly differed between cancer type (GU 86%, breast 96%, GI 22%, p<0.001). Cumulative incidence of late grade >2 toxicity was 1.2%, with 1 patient experiencing late grade 3 toxicity, and no grade 4-5 acute or late toxicities. HRQOL declined from mean (standard deviation) of 66.9 (20.2) at baseline to 60.5 (22.2) at 6 months, which did not meet the threshold for a minimal clinically important difference. ConclusionsSBRT for OP metastases delayed change in ST in approximately half of patients, warranting investigation in randomized trials.