OligoCare TwiCs (Trials Within Cohorts) Trial Comparing Acute Toxicity in Single-fraction vs Multiple-fraction SBRT for Metastasis-directed Treatment (SPRINT)

Inclusion Criteria: * Patient is part of the RP1822-OligoCare. As in OligoCare, ALL active cancer lesions (loco-regional primary and all oligometastases) were or will be treated with radical intent (surgery or radiotherapy). * All lesions that will be treated with radical radiotherapy have to be amenable to single-fraction SBRT. Concurrent systemic treatment is allowed. * Written informed consent must be given according to ICH/GCP, and national/local regulations. Patients will be consented in a step-wise approach. Step 1 \[both control and experimental arms\]: patients will need to consent to be included and evaluated in E²-RADIatE (that includes the non-interventional OligoCare prospective registry cohort) and to potentially be randomized to future sub-studies for which they are eligible; no further consent will be sought if they are randomized to the SoC (control) arm; Step 2 \[experimental arm only\]: if eligible for the current sub-study and randomized to receive single-fraction SBRT, patients will need to consent to receiving the experimental treatment. Exclusion Criteria: All targeted lesion judged by the treating physician to be associated with risks for severe toxicity following single-fraction SBRT. The following lesions are systematically excluded: * Pulmonary metastases within 1 cm of proximal bronchial tree, esophagus or brachial plexus * Metastases within \< 5 mm of any hollow GI structure: esophagus, stomach, small bowel, large bowel * Metastases within \< 5 mm of the spinal cord, the cauda equina or the brachial plexus * Metastases \> 5 cm in largest diameter.