The Impact of Body Weight Status at the Time of Diagnosis on Colorectal Cancer Treatment Outcomes

Colorectal cancer is the second leading cause of cancer-related deaths for both men and women in the United States (Siegel et al. 2012). There are approximately 140,000 new cases each year, and approximately 55,000 deaths. The 5-year survival rate is approximately 65%. There has been a slow decreasing trend in mortality due to increases in early detection and screening. In fact, it is estimated that the mortality rate could be decreased by 50% if early detection and removal of adenomatous polyps were conducted more often for those individuals at risk. Among the numerous risk factors associated with colorectal cancer (age, family history, smoking, alcohol consumption, nutritional, physical activity and obesity), obesity is a leading modifiable risk factor. In the United States alone, the Centers for Disease Control and Prevention reported that approximately 66% of adults are overweight as defined by body mass index (BMI), with approximately 31% of adults classified as obese (Hedley et al. 2004). While the association between obesity and many chronic diseases is well-established, the association between obesity and cancer is becoming increasingly recognized. Relative to other cancers, obesity appears to be closely associated with the development of colorectal cancer, in particular (Rickles et al. 2013; Jafri and Mills. 2013; Ma et al. 2013). At the same time, the mechanisms for this association have not been fully determined. Inflammatory cytokines, adipokines, insulin, and estrogen, have all been suggested as potential mediators of the association between obesity and colorectal cancer development (Guffey et al. 2013). While many studies have reported a positive correlation between obesity and the risk of colorectal cancer, the literature is only beginning to accumulate on the impact of obesity on cancer prognosis, an even less understood area of investigation. The goal of this study is to add to the literature describing the associations between obesity at the time of diagnosis and colorectal cancer treatment outcome results. Specifically, we examined whether or not obesity is associated with more aggressive disease and all-cause and cancer-specific survival. In addition to using BMI as a measure of obesity, we have data on a novel but validated method to measure body composition called bioelectrical impedance analysis (BIA). This assessment was systematically conducted at the Cancer Treatment Centers of America hospitals in patients at risk of weight-related morbidity. To our knowledge, limited data has been published in the literature using this method to assess the association between obesity and cancer treatment outcomes following diagnosis.