Prognostic value of low psoas muscle mass in patients with cervical spine metastasis.

Morphometric analyses have shown that the psoas muscle mass is associated with mortality in cancer patients. Because of the low incidence of cervical spine metastasis, few studies have been reported in this population. The present study aimed to identify the prognostic value of a psoas muscle mass in predicting overall survival. We also evaluated factors associated with surgical intervention for cervical spine metastases. We retrospectively evaluated 97 patients (mean age 65.2 years) diagnosed with cervical spine metastases between February 2009 and July 2016. The psoas muscle area was measured at the L3 level on computed tomography at the time nearest the diagnosis of cervical spine metastasis. Cox proportional hazards analyses were performed to evaluate the relation between overall survival and the psoas muscle's composition. The mean overall survival for patients who underwent surgery was not significantly different from that for those without surgery. Multivariate analyses showed that the lowest percentage quartile (0%-25%) of the psoas muscle mass was associated with poor overall survival after adjusting for age and the prognostic predictive value (hazard ratio 1.93, 95% confidence interval 1.12-3.32; p = 0.017). Spinal cord compression, spinal instability, palsy, and the poor prognostic predictive value were factors associated with surgical intervention. In conclusion, a psoas muscle mass in the lowest quartile was independently associated with shorter survival among patients with cervical spine metastases. Although the poor prognostic predictive value was associated with surgical treatment, the overall survival was not different between patients who did or did not undergo surgery.