Primary Stereotactic Body Radiation Therapy for Breast Cancer Spinal Metastases.

Abstract

Background: To present insights gained from a decade of employing stereotactic body radiation therapy (SBRT) as a primary intervention for spinal bone metastasis (SBM) originating from breast cancer (BC).

Methods: We retrospectively examined the application of primary SBRT (the CyberKnife System) for BC SBMs between March 2012 and January 2023.

Results: We recruited 47 female patients with 82 SBMs affecting 104 vertebrae. The mean age was 53.2 ± 12.7 years. The overall local control (LC) rate of primary SBRT for BC SBMs was 84.1%. The median local progression (LP) occurred at 12 (3-66) months. The LP rates were 9.7%, 13.3%, and 18.3% at 1, 3, and 5 years following SBRT. We observed a lower LC rate in White patients than that in Asian patients. Factors associated with an increased risk of LP included SBMs from invasive lobular carcinoma, and patients with lower revised Tokuhashi scores. Additionally, the 1-, 3-, and 5-year LP rates of different SFED (≥20 Gy vs. <20 Gy) were 4.3% versus 19.1%, 7.2% versus 24.0%, and 11.5% versus 28.9%. The incidence of acute local adverse events (AEs) was 24.4% and was significantly associated with advanced age and prescribed target coverage of less than 95%.

Conclusions: We have demonstrated SBRT using the CyberKnife System as an effective primary intervention for BC SBMs. Our findings underscore the importance of treatment planning to optimize outcomes and minimize AEs in patients undergoing SBRT for SBMs.