The impact of systemic and radiation therapy in patients undergoing spine surgery for metastatic breast cancer: a dual-institution study

OBJECTIVE Although targeted systemic therapies and postoperative radiation therapy (RT) have improved outcomes in patients with metastatic breast cancer, how treatment combinations impact spine surgery outcomes remains understudied. In patients undergoing spine surgery for metastatic breast cancer, the authors sought to do the following: 1) describe patterns of postoperative therapy; 2) report perioperative outcomes; and 3) evaluate the impact of the treatment plan on local recurrence (LR) and overall survival (OS). METHODS A dual-institution, retrospective cohort study of patients undergoing spine surgery for metastatic breast cancer was undertaken. Patients were divided into 4 groups based on the postoperative treatment: systemic therapy alone, RT alone, combined, or neither. Patients were also classified by their breast cancer molecular subtype: HR+/HER2+, HR+/HER2−, HR−/HER2+, or TNBC. Preoperative data were used to calculate commonly cited spine surgery prognostic scores. Perioperative and survival outcomes were evaluated. Chi-square, ANOVA, log-rank, and Cox regression tests were performed. RESULTS In this cohort of 66 patients undergoing spine surgery for metastatic breast cancer, the majority received combined systemic therapy and RT (59.1%), with fewer receiving systemic therapy alone (18.2%), RT alone (7.6%), or neither (15.2%). There was a significant difference based on the type of postoperative therapy in having a motor deficit on presentation (p = 0.004; V = 0.448), preoperative Karnofsky Performance Scale score (p = 0.012; η² = 0.160), and preoperative American Spinal Injury Association Impairment Scale score (p = 0.015; V = 0.329). Patients who received RT alone or neither therapy presented at a higher rate with a motor deficit and tended to have worse preoperative Karnofsky Performance Scale and American Spinal Injury Association Impairment Scale scores compared to those who received combined or systemic-only treatment. No significant differences in prognostic scores were detected between molecular subtypes. Patients who underwent any postoperative treatment had a longer OS (combined, 4.23 years; systemic, 3.78 years; RT, 5.15 years) than patients who received neither (0.26 years). No significant difference was observed in LR. Multivariable Cox regression revealed that any adjuvant treatment significantly improved survival compared to no treatment: combined, hazard ratio 0.041 (95% CI 0.009%–0.169%), p < 0.0001; systemic, hazard ratio 0.073 (95% CI 0.016%–0.316%), p = 0.0006; and RT, hazard ratio 0.139 (95% CI 0.016%–0.848%), p = 0.0431, whereas readmission within 90 days following surgery significantly worsened survival: hazard ratio 5.372 (95% CI 1.753%–15.895%), p = 0.0024. CONCLUSIONS In this dual-institution study of patients undergoing spine surgery for metastatic breast cancer, any treatment with systemic therapy and/or RT was associated with improved OS but not LR. Spine surgeons should work collaboratively with oncologists and radiation oncologists to ensure that treatment is started as soon as safely possible after surgery.