Aim To evaluate real-world local control outcomes and identify clinical and dosimetric determinants of local progression following metastasis-directed stereotactic ablative radiotherapy (SABR) within the international OligoCare cohort. Methods OligoCare is a prospective observational registry (EORTC-ESTRO E2-RADIatE) evaluating SABR for oligometastatic prostate, breast, colorectal, and non-small cell lung cancer (NSCLC). The secondary endpoint, local progression, was defined as recurrence within the planning target volume (PTV), with death treated as a competing risk. Multivariate analyses were performed at both the patient and lesions levels (restricted to single-lesion patients) to account for confounding factors. Results Between July 2019 and July 2025, 2,805 eligible patients were enrolled. Of these, 2,447 from 57 institutions received the recommended protocol treatment and were included in the analysis (median follow-up 31 months). The distribution of primary tumors was prostate (41.7%), NSCLC (21.7%), colorectal (21.2%), and breast (15.4%). The 1- and 3-year local progression rates were 5.0% and 11.4%, respectively. Among single-lesion patients (n = 1,714), a higher PTV minimum dose was the sole independent predictor of local control, with an 11% risk reduction per 10 Gy EQD2 increase (HR 0.89 97.5% CI 0.82-0.98, p = 0.005). Although de novo OMD showed better local control compared to repeat OMD in the patient-level analysis (HR0.65 97.5% CI 0.47-0.91, p = 0.004), this effect was largely driven by higher dose delivery in de novo cases. Colorectal primaries faced a significantly higher risk of progression than prostate cancer (HR 2.63 97.5% CI 1.71-4.05, p < 0.001), despite receiving the highest dose per fraction. Conclusion SABR provides durable real-world local control in oligometastatic disease. Optimizing the minimum PTV dose appears the most critical technical factor for success. The inferior local control observed in colorectal metastases suggests a combination of treatment intensity challenges and intrinsic radioresistance, which could guide future trial design and dose-escalation strategies.
Joye et al. (Thu,) studied this question.