Prognostic significance of the skeletal muscle index and an inflammation biomarker in patients with breast cancer who underwent postoperative adjuvant radiotherapy

Background: Given the growing evidence that sarcopenia and inflammation influence the survival of patients with cancer, we evaluated the prognostic significance of the skeletal muscle index (SMI) combined with an inflammation marker in patients with breast cancer who underwent postoperative adjuvant radiotherapy. Methods: We conducted a retrospective analysis of 301 patients with breast cancer who received postoperative adjuvant radiotherapy between 2010 and 2012. The SMI was measured using preradiotherapy computed tomography (CT) simulation images at the level of the fourth thoracic vertebra (T4). Receiver operating characteristic curve analyses were used to determine the optimal cutoff values for the SMI and inflammatory marker. Patients were divided into 2 groups (high SMI and low SMI), based on the SMI cutoff of 10.57 cm2/m2. Results: Patients in the high-SMI group had a median overall survival (OS) of 62.4 months, which was significantly shorter than those in the low-SMI group, with a median OS of 68.5 months (P = 0.025). Patients in the high-SMI group had a median recurrence-free survival (RFS) of 62.3 months, which was shorter but not significantly than the median RFS of 65.2 months of the low-SMI group (P = 0.159). Univariate and multivariate survival analyses revealed SMI was an independent predictor of OS (P = 0.044). The SMI-MLR combination was found to be an independent predictor of OS (P = 0.006) and RFS (P = 0.009). Conclusions: The current findings support the SMI as a promising indicator for predicting clinical outcomes in patients with breast cancer receiving postoperative adjuvant radiotherapy. A high SMI accompanied by systemic inflammation was significantly associated with reduced OS and RFS.