Abstract
Background/Objectives: Inadequate dosing and respiratory motion contribute to local recurrence for oligometastatic disease (OMD). While short-term LC rates are well-documented, data on long-term LC remain limited. This study investigated long-term LC after stereotactic body radiotherapy (SBRT), using respiratory motion management techniques. Methods: This retrospective study took place at UZ Brussel with follow-up until Oct 2024. It analyzed oligometastatic patients treated with SBRT between Jul 2012 and Feb 2017. Treatment involved delivering 50 Gy in 10 fractions on the 80% isodose line, building on data from a prior prospective study. Lesion movement was managed using internal target volume (ITV) or dynamic tumor tracking (DTT) with marker. The primary endpoint of the study was long-term LC and identifying variables associated with it using a Cox proportional hazards model. Results: A total of 100 patients were treated for a total of 211 metastatic lesions. Lesions were predominantly in the lungs (74%) and treated using ITV (88%). LC rates at 1, 3, 5, and 10 years were 76.5%, 53.8%, 38.1%, and 36.3%, respectively. Improved LC was observed in locations other than lung and liver (HR: 0.309; p = 0.024) and with increasing age (HR: 0.975; p < 0.010). Worse LC was seen in liver lesions (HR: 1.808; p = 0.103) and systemic therapy post-radiotherapy (HR: 3.726; p < 0.001). No significant associations were found with tumor size or tumor motion, nor between the two motion management strategies used (DTT and ITV). Conclusions: Appropriate motion management is key in LC for OMD. No significant difference in LC was found between both techniques. Lesion location, patient age, and systemic therapy post-radiotherapy were prognostic factors for LC.