Stereotactic body radiotherapy results for de-novo extracranial oligometastatic cancer patients.

Background: The aim of study was to evaluate the oncological results of stereotactic body radiotherapy (SBRT) in de-novo oligometastatic (dOM) disease.

Materials and methods: Patients who underwent SBRT for dOM disease in Radiation Oncology Clinic of XXX Hospitals were analyzed retrospectively. The endpoints of the study were overall survival (OS) and disease free survival (DFS).

Results: 84 patients with treated between 08.06.2019-15.11.2022 were analyzed. The median follow up was 26 (range 6-219) months. dOM subgroups were as follows: 37 (44.0%) synchronous dOM (sdOM); 31 (37%) metachronous oligorecurrence (mdOR) and 16 (19.0%) metachronous oligoprogression (mdOP). Grade 1 acute side effects (ASE) were observed in only 1 patient and no grade ≥ 2 a ASE were observed. Progression was observed in 45 (53.6%) of the patients. The median DFS was 8 (range 1-32) mo, 1y DFS was 44.5%; 2y DFS was 26.2%. Significantly higher DFS was obtained in mdOR than sdOM and mdOP [p = 0.020; hazard ratio (HR): 1.6; 95% confidence interval (CI): 0.75-3.68%]. The relationship between response assessment after SBRT and DFS was significant (p < 0.001; HR: 4.8; 95% CI: 1.9-12.2). Twenty-nine (34.5%) patients were ex and 55 (65.5%) were alive. 1y OS was 75.6%; 2y OS -61.2%; 3y OS -57.4% and the median OS value has not yet been reached. Lower OS was observed in sdOM compared to mdOP and mdOR (p = 0.035, HR: 0.45; 95% CI: 0.21-0.96). The relationship between response assessment after SBRT and OS was significant (p = 0.017; HR: 6.6; 95% CI: 1.7-25.7).

Conclusion: Higher DFS was observed in mdOR patients and lower OS was observed in sdOM patients. SBRT response in dOM patients may be a prognostic factor for DFS and OS.