Explaining the obesity paradox: The association between body composition and colorectal cancer survival (C-SCANS study)

Abstract

Background

Body composition may partially explain the U-shaped association between BMI and colorectal cancer (CRC) survival.

Methods

Muscle and adiposity at CRC diagnosis and survival were examined in a retrospective cohort using Kaplan Meier curves, multivariable Cox regression, and restricted cubic splines in 3,262 early stage (I-III) male (50%) and female (50%) patients. Sarcopenia was defined using optimal stratification and sex- and BMI-specific cut points. High adiposity was defined as the highest tertile of sex-specific total adipose tissue (TAT). Primary outcomes were overall mortality (OM) and CRC specific mortality (CRCsM).

Results

Forty-two percent of patients were sarcopenic. During 6.0 years of follow-up, 788 deaths occurred, including 433 from CRC. Sarcopenic patients had a 27% (HR 1.27; 95% CI 1.09, 1.48) higher risk of OM, than those who were not sarcopenic. Females with both low muscle and high adiposity had a 64% higher risk of OM (HR 1.64; 95% CI 1.05, 2.57) when compared to females with adequate muscle and lower adiposity. The lowest risk of OM was seen in patients with a BMI between 25-<30-kg/m ², a range associated with the greatest number of patients (58.6%) who were not at increased risk of OM due to either low muscle or high adiposity.

Conclusions

Sarcopenia is prevalent among non-metastatic CRC patients, and should, along with adiposity be a standard oncological marker.

Impact

Our findings suggest a biological explanation for the obesity paradox in CRC and refute the notion that the association between overweight and lower mortality is due solely to methodological biases.