In our model (for spinal metastasis), multivariable analysis showed that the serum level of irisin has a protective role for spinal metastasis in breast cancer patients after adjusted for age and BMI (crude odds ratio [OR], 0.850, [95% confidence interval, CI 0.746–0.968]; adjusted OR, 0.873 [95% CI 0.764–0.999]). The gene discussed is FNDC5; the disease is breast cancer.