Sarcopenia is associated with poor prognosis in patients with colorectal cancer (CRC), but the mechanisms contributing to this association remain unclear. We hypothesized that skeletal muscle status is associated with tumor-infiltrating lymphocytes (TILs) in patients with CRC. Therefore, this study investigated the clinical effect of sarcopenia and its relationship with the local immune system in CRC patients.

Our data showed an association between skeletal muscle status and local immune cells, and this association may play a pivotal role in the clinical outcome of patients with CRC.

A total of 256 consecutive patients with CRC who underwent curative resection between 2008 and 2014 were enrolled. Sarcopenia was determined according to the skeletal muscle index (SMI), which was assessed using L3 skeletal muscle mass on axial computed tomography images, and its relationship with patient clinicopathological characteristics and survival was evaluated. Additionally, TILs (CD3+, CD8+, CD4+, and FOXP3+ T cells) were assayed by immunohistochemistry. The relationship between TILs and skeletal muscle status was evaluated.

Patients with a lower SMI showed significantly shorter recurrence-free and overall survival compared with those with a higher SMI. Low expression of TILs was associated with significantly shorter recurrence-free survival. SMI was significantly correlated with the number of CD3+ and CD8+ cells in the ordinal logistic regression analysis. Patients with low skeletal muscle status and low CD3+ and CD8+ cells had an unfavorable prognosis compared with patients with high skeletal muscle status and high CD3+ and CD8+ cells.