Biomarkers in Spinal Metastasis of Breast Cancer: Insights Into Survival and Functional Outcomes

Breast cancer is the most common malignancy in females, with osseous metastasis predominantly occurring in the spine. We investigated the prevalence of mutations in patients with metastatic breast cancer to the spine (MBCS) and evaluated genotypic and therapeutic prognostic factors associated with survival.

The medical records and molecular genetic profiles of 50 patients diagnosed with MBCS at a single comprehensive cancer center between May 2013 and October 2022 were reviewed retrospectively. Data on demographics, biomarkers from genetic sequencing and immunohistochemistry, and anticancer therapies were collected. Overall survival rates were calculated, and accelerated-failure-time (AFT) models were used to identify prognostic factors for survival.

The median overall survival time was approximately 6 years. Ninety-nine biomarkers were identified, with the estrogen receptor (ER) (38.4%), GATA protein binding 3 (32.3%), progesterone receptor (28.3%), human epidermal growth factor receptor 2 (13.1%), and AE1/AE3 (8.1%) being the most common. ER⁺ was the only biomarker associated with better survival when accounting for smoking status and treatment in an AFT model. Worse survival was associated with a smoking history (time ratio [TR]=0.427, p=0.043) and immunotherapy or targeted therapy (TR=0.440, p=0.048), but not radiotherapy of spinal metastasis (TR=0.256, p=0.121). In an alternative AFT model, better survival was associated with eribulin (TR=3.374, p=0.009), whereas worse survival was associated with pertuzumab (TR=0.390, p=0.010) and capecitabine (TR=0.496, p=0.024).

Only ER expression was associated with the overall survival time when other confounding factors such as smoking status and treatment type were considered. A smoking history was associated with shorter survival, while eribulin was associated with survival prolongation.