Trends in Survival After Surgery for Breast Cancer Metastatic to the Brain and Spinal Column in Medicare Patients: A Population-Based Analysis

BACKGROUND: Central nervous system (CNS) metastases are a common occurrence in patients with breast cancer and are identified in up to 30% of patients at autopsy. OBJECTIVE: To determine population-based estimates of survival times after surgical intervention for Medicare patients with metastatic breast cancer to the brain and spinal column. METHODS: Female breast cancer patients with metastases to the brain and spinal column and undergoing neurosurgical treatment were identified through the Surveillance, Epidemiology, and End Results-Medicare database. Estimates of survival were calculated with Kaplan-Meier estimation and a Cox proportional hazards model. RESULTS: There were 643 patients who underwent neurosurgical treatment of metastatic disease from 1986 to 2005. Of these patients, 264 underwent cranial surgery and 379 underwent spinal surgery. There were 40 deaths during the postoperative hospital admission for an inpatient postoperative death rate of 6.2%. Inpatient death has declined by approximately 50% for surgeries performed in the most recent decade; however, the 30-day mortality rate of 9.0% has remained constant. The median postoperative survival after cranial surgery was 7.8 months (95% confidence interval, 6.2-9.2), after laminectomy was 9.4 months (95% confidence interval, 6.3-15.7), and after spinal fusion was 15.7 months (95% confidence interval, 11.9-18.5). Survival after spinal fusion has increased by approximately 50% in the recent decade. Patients with increased survival after cranial surgery were younger, had fewer comorbidities, and had longer periods from breast cancer diagnosis to surgery. Patients with increased survival after spinal neurosurgery had lower-grade lesions and longer time periods from breast cancer diagnosis to surgical treatment. CONCLUSION: After surgically treated metastases, one-third of cranial patients and one-half of spinal patients are alive at 1 year. The overall postoperative survival has increased over time only for spinal fusion procedures.