Prognostic value of skeletal muscle index and monocyte-to-lymphocyte ratio for lymph node-positive breast cancer patients after mastectomy

Background: We aimed to assess the prognostic value of the skeletal muscle index (SMI) and monocyte-to-lymphocyte ratio (MLR) in lymph node-positive breast cancer patients after mastectomy. Methods: We enrolled female lymph node-positive breast cancer patients who had undergone mastectomy between January 2011 and December 2013 with lymph node metastasis. Skeletal muscle tissue was measured using computed tomography (CT), and the patients were grouped based on the receiver operating characteristic curves to obtain the cut-off point for SMI; similarly, the optimal cutoff point for the MLR was obtained. Survival analysis was chiefly performed to determine overall survival (OS) among the patients. Results: The median age of the 97 included patients was 46 years (range, 27-73 years), whereas the median follow-up duration was 62.5 months. Of these patients, 71 exhibited low SMI and 66 exhibited high MLR. Kaplan-Meier curves indicated that low SMI (5-year OS, 97.2% vs. 84.6%; log-rank P=0.021) and low MLR (5-year OS, 98.5% vs. 83.9%; log-rank P=0.004) were associated with better OS. Moreover, patients with both high SMI and MLR (high SMLR) had significantly worse OS (5-year OS, 66.7% vs. 96.6%; log-rank P<0.001), relative to the low SMLR group. Multivariate analysis indicated that patients with low SMI had a lower overall dying risk, relative to those with high SMI [hazard ration (HR), 0.188; P=0.038], whereas patients with high MLR had a higher risk of death as compared to those with low MLR (HR, 7.152; P=0.021). Furthermore, SMLR was an independent prognostic factor of poor OS (HR, 13.272; P=0.001). Conclusions: Low SMI and low MLR are both associated with better OS in lymph node-positive breast cancer patients after mastectomy. SMI combined with MLR (SMLR) may be powerful prognosis factor for OS among these patients.