Adiposity in resectable colorectal cancer.

Abstract

3614 Background: Sarcopenia and myosteatosis affect survival in colorectal cancer (CRC). The role of adiposity is not yet fully elucidated. This study explores visceral and subcutaneous adipose tissue (VAT/SAT) distributions, and how they affect overall (OS), disease-free (DFS) and cancer specific survival (CSS). Methods: This retrospective cohort study, included resected stage I-III CRC in Alberta from January 2007 to December 2009. We excluded recurrent/metastatic disease or no CT scan. This study was approved by the Health Research Ethics Board at the University of Alberta. Body composition parameters were measured from CT scans. Sarcopenia and myosteatosis were defined by cohort-specific cut-off values. Total and visceral fat areas were indexed by height, and cohort-specific cut-offs defined total and visceral obesity (VO). SAT (SC:TFR) and VAT (V:TFR) to total adipose ratios were compared by gender, as described by Fleming. SAT and VAT fat radiodensity (Hounsfield units, HU) was measured and divided into quartiles. Differences between groups were compared with student’s t-test and Fisher Exact test. Cox proportional hazard models were created, adjusting for important covariates, to assess adiposity effects on OS, DFS and CSS. Results: Our cohort included 968 patients with a median follow up of 63.5 months. The majority were stage II (38.6%) and III (51.0%). In total, 67.9% had total obesity and 51.0% had visceral obesity. In males, there was no difference in the incidence of myosteatosis or sarcopenia, regardless of V:TFR or SC:TFR. In women, those with a high V:TFR or SC:TFR had significantly higher incidence of myosteatosis, but not sarcopenia. Men and women with elevated V:TFR had significantly lower VAT and SAT HU (p<0.001, p=0.0113). Those with elevated SC:TFR had significantly higher VAT and SAT HU (p<0.001). VAT and SAT HU was lowest in those with myosteatosis alone (p<0.001; p=0.005). In survival analysis, VO and VAT HU quartiles predicted worse OS in uni-, but not multivariate analysis. SAT HU quartiles predicted worse survival in uni- and multivariate analysis, with the highest quartile of SAT HU predicting increased risk of death (HR 1.35, p=0.037). Adiposity was not predictive of CSS or DFS in uni- or multivariate analysis. Conclusions: This study demonstrated changes in VAT/SAT in relation to well described body composition parameters. SAT HU may have a more important role in OS than visceral adipose characteristics, despite known metabolic characteristics of VAT. True roles of adipose tissue in CRC outcomes remains unclear. VAT/SAT measurements using cross-sectional imaging allows for a detailed analysis and understanding of how adiposity may affect survival. [Table: see text]