Sarcopenia supersedes subjective global assessment as a predictor of survival in colorectal cancer

Background Sarcopenia, the presence of skeletal muscle mass depletion, can be objectively quantified, whereas subjective global assessment (SGA) is a widely utilized subjective instrument to assess nutritional status. Both the presence of sarcopenia and SGA-assessed malnutrition, in isolation, have been shown to be associated with worse overall survival in a wide range of cancers. However, there is no research evaluating the independent prognostic significance of both the presence of sarcopenia and malnutrition as part of the same analysis. We investigated the impact of sarcopenia on overall survival in colorectal cancer specifically controlling for malnutrition. Methods We examined a consecutive case series of 112 patients with colorectal cancer first seen at our institution between August 2012 and October 2017. Using computed tomography (CT) imaging, the cross-sectional area of muscles at the L3 vertebral level was measured and then divided by height squared to calculate skeletal muscle index (SMI). Sarcopenia was defined as SMI ≤38.5 cm2/m2 for women and ≤52.4 cm2/m2 for men. SGA assessments were completed within 2 weeks of CT imaging. The association of sarcopenia and malnutrition with overall survival was assessed using univariate and multivariate Cox regression analysis. Results Median age at presentation was 53.3 years. Sixty-six (58.9%) patients had metastatic disease at diagnosis. Using SMI, 46 (41.1%) patients were sarcopenic, while 66 (58.9%) were non-sarcopenic. Using SGA, 69 (61.6%) patients were assessed as well-nourished, while 43 (38.4%) were malnourished. Of 69 patients classified as well-nourished by SGA, 22 (31.9%) were sarcopenic. Similarly, of 43 patients categorized as malnourished by SGA, 19 (44.2%) were non-sarcopenic. On multivariate analysis, after adjusting for age, gender, tumor stage, BMI, treatment history and SGA, patients with sarcopenia had 3 times greater risk of mortality compared to those without sarcopenia (p = 0.001). The median survival of patients with both sarcopenia and malnutrition (n = 24) was 14.6 months (95% CI: 10.5 to 18.6) compared to the median survival of 25.9 months (95% CI: 7.8 to 44.0) in patients who were either sarcopenic or malnourished but not both (n = 41; p = 0.001). The median survival of patients who were non-sarcopenic and well nourished (n = 48; p = 0.001) was 38.6 months (95% CI: 25.6 to 51.6). Conclusions The exploratory study suggests that presence of sarcopenia supersedes the presence of malnutrition as a predictor of survival in colorectal cancer. Co-existence of sarcopenia and malnutrition is associated with worse survival in colorectal cancer compared to just one of those conditions being present. Prospective studies with large sample sizes are needed to confirm these findings.