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Study Design: Retrospective cohort study.

Objective: Spinal metastases are common in patients with breast cancer, and accurate estimation of postoperative survival is crucial for selecting appropriate candidates for metastasis surgery. This study investigated the association between breast cancer subtype, according to the St. Gallen classification, and survival after surgery for spinal metastases with the aim of improving prognostic assessment and supporting informed patient counselling.

Methods:: This study included 110 patients with breast cancer who underwent surgery for spinal metastases identified from the Swedish Spine Register and the Swedish National Quality Register of Breast Cancer. Patients were categorized in terms of the breast cancer subtype according to the St. Gallen classification. Postoperative survival was analysed using Kaplan-Meier estimates and a Cox proportional hazards model.

Results: The overall median survival following spinal surgery was 25 months (95% CI 19-31), while the median postoperative survival by subtype was 39 months (95% CI 28-50) for luminal A patients, 20 months (95% CI 9-31) for luminal B patients, and 48 months (95% CI 20-76) for luminal B/HER2+ patients. The median survival was not reached for the nonluminal HER2+ group, whereas patients with triple-negative breast cancer had a median survival of only 5 months (95% CI 4-6). The St. Gallen subtype was significantly associated with postoperative survival according to univariable (P<0.001) and multivariable analyses (P = 0.011).

Conclusions: Breast cancer subtype according to the St. Gallen classification was significantly associated with survival after surgery for spinal metastases. These findings indicate that the St. Gallen classification may serve as a valuable prognostic tool in the metastatic spine setting. Incorporation of molecular subtype information may improve estimation of postoperative survival and support informed patient counselling, expectation management, and individualized surgical decision-making in patients with breast cancer spinal metastases.