Dose-intensified SBRT for vertebral oligometastases: results from a prospective clinical trial

Purpose: To prospectively evaluate safety and efficacy of dose-intensified multifraction SBRT using a simultaneous-integrated boost concept for vertebral oligometastases. Material and Methods: Data from 128 patients with 143 vertebral oligometastases (≤5 distant metastases in total) treated with dose-intensified SBRT (48.5 Gy/10 [with epidural involvement] or 40 Gy/5 [without epidural involvement]) in the randomized and non-randomized arms of a phase 3 clinical trial conducted at 18 international centers between 2016 and 2023 were analyzed. Results: The median age of all patients was 68 years; 77 patients (60.2%) had breast and prostate cancer. Of 143 vertebral metastases, 23 (16.1%) and 22 metastases (15.4%) had epidural and paraspinal tumor involvement, respectively. The median follow-up time was 24 months. At 2 years, cumulative incidence of local failure (4 failures) was 5.3%. There were 4 (2.8%) baseline and 8 (5.6%) de novo vertebral compression fractures (VCFs). Two-year OS was 82.2% (95% CI, 74.9–89.6%). There was no grade ≥ 4 adverse events (AE) and the crude rate of grade 3 AEs was 5.5%; no myelopathy or plexopathy was observed. On multivariate analysis, only non-breast or non-prostate cancer (HR, 7.91; 95%, CI 1.79–35.03; 2-sided P = 0.01) were found to be prognostic for adverse OS. No prognostic factors for VCF were identified. Epidural and paraspinal involvement were not found to be prognostic for treatment outcome. Conclusions: Dose-intensified SBRT for vertebral oligometastases is effective and safe, even in high-risk patients with epidural or paraspinal involvement.