BackgroundThe impact of sarcopenia on the outcome of patients with left-sided colon and rectal cancer has not been exhaustively investigated. Thus, the present study was performed to evaluate the effect of sarcopenia on the outcome of patients with left-sided colon and rectal cancer.MethodsPatients with pathologically diagnosed stage I, II and III left-sided colon or rectal cancer who had undergone curative surgery between January 2008 and December 2014 were retrospectively reviewed. The psoas muscle index (PMI) identified by 3D-image analysis of computed tomographic images was the criterion used to diagnose sarcopenia. The cut-off value recommended by Hamaguchi (PMI value < 6.36 cm2/m2for men and < 3.92 cm2/m2for women) was adopted to confirm the diagnosis of sarcopenia. According to the PMI, each patient was divided into the sarcopenia group (SG) or the nonsarcopenia group (NSG). Then, the SG was compared with the NSG in terms of postoperative outcomes.ResultsAmong the 939 patients included, 574 (61.1%) were confirmed to have preoperative sarcopenia. Initially, it was demonstrated that the SG was not significantly different from the NSG in terms of most baseline characteristics except for a lower body mass index (BMI) (P< 0.001), a larger tumour size (P< 0.001) and more weight loss (more than 3 kg in the last three months) (P= 0.033). The SG had a longer hospital stay after surgery (P= 0.040), more intraoperative blood transfusions (P= 0.035), and higher incidence of anastomotic fistula (P= 0.027), surgical site infection (SSI) (P= 0.037) and hypoalbuminemia (P= 0.022), 30-day mortality (P= 0.042) and 90-day mortality (P= 0.041). The SG had significantly worse overall survival (OS) (P= 0.016) and recurrence-free survival (RFS) (P= 0.036) than the NSG. Subsequently, Cox regression analysis revealed that preoperative sarcopenia was an independent predictive factor for worse OS (P= 0.0211, HR = 1.367, 95% CI: 1.049–1.782) and RFS (P= 0.045, HR = 1.299, 95% CI: 1.006–1.677).ConclusionPreoperative sarcopenia adversely affects the outcome of patients with left-sided colon and rectal cancer, and preoperative nutrition supplementation may help us improve their long-term and short-term outcomes.