The Role of Spinal Stereotactic Radiosurgery for Patients with Breast Cancer Metastases

Introduction: Primary breast cancer metastases to the spine are associated with low quality of life and poor survival. Radiosurgery has an increasing role in this patient population. This single-institution study analyzed the long-term role of spinal stereotactic radiosurgery (SSRS) in treating spine metastases from primary breast cancers.

Methods: Ninety patients (89 female) were treated with SSRS between 2003-2023 for 155 primary breast spinal metastases (228 treated vertebral levels). The median age at SSRS was 57 years (range: 35-88), and the median KPS at SSRS was 80 (range: 40-100). Seventy-five (48%) lesions had epidural involvement, and 79 (51%) lesions were classified as potentially unstable or unstable using the Spinal Instability Neoplastic Score (SINS). Forty-two (27%) lesions were treated initially with surgical decompression. The median tumor volume per lesion was 26.3 cc (range: 2-197), and the median single-fraction prescription dose was 17 Gy (range: 12-25).

Results: The median follow-up for the cohort was 15 months. Post-SRSS, 7 (4%) lesions progressed locally at a median of 29 months (range: 4-70). The 1-, 2-, and 5-year local tumor control rates per lesion were 98%, 97%, and 92%, respectively. On univariate analysis, no prognostic factors were significantly correlated with local tumor control. The median overall survival was 32 months (range: 2-183). The 1-, 2-, and 5-year overall survival rates were 72%, 53%, and 30%, respectively. On univariate analysis, only KPS ≥ 80 at first SSRS (p=0.009, HR: 0.51, 95% CI: 0.31-0.84) was significantly associated with improved overall survival. Pain was associated with 125 (81%) lesions pre-treatment. Patient-associated pain improved for 78 lesions (68%), was stable for 33 lesions (29%), and progressed for 3 lesions (3%). Mild radiation toxicities were reported in 17 (11%) cases.

Conclusion : Spinal radiosurgery is a safe and highly effective long-term treatment modality for spine metastases from primary breast cancers.