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Abstract 79: The relationship between abdominal fat distribution, vitamin D levels, and physical activity in colorectal cancer patients: A pilot study.

Abstract Introduction: Abdominal obesity, low physical activity and low levels of Vitamin D (Vit D) are associated with an increased risk for colorectal cancer (CRC). Physical inactivity contributes to obesity – an emerging global health burden. Individuals with the same body mass index (BMI) may vary in the distribution of subcutaneous and visceral abdominal fat. Subcutaneous and visceral fat differ in their metabolic functions. Moreover, Vit D is metabolized in adipose tissue; however, it is unclear if Vit D levels are influenced by the amount and the distribution of adipose tissue. Decreased levels of Vit D are found in obese subjects and a positive association between physical activity and Vit D levels is currently discussed. It is still unknown how this triangle relationship is displayed in CRC patients and how it might influence the course of disease. Thus, within this pilot study we explored the relationship between abdominal fat distribution, plasma levels of Vit D, and metabolic equivalent of task (MET) level as a marker for intensity and energy expenditure of physical activity in CRC patients. Methods: This pilot study was conducted on 194 CRC patients from the ColoCare Study, a cohort of newly-diagnosed stage I-IV CRC patients (age>18). Plasma 25(OH)VitD3 levels were measured by LC/MSD. BMI was calculated (kg/m2) and the absolute abdominal fat and the distribution of subcutaneous and visceral abdominal fat was assessed by abdominal computed tomography (CT) scans. The total (TFA), subcutaneous (SFA) and visceral fat area (VFA) is presented as an area (cm2) on level L3/L4. To assess physical activity we calculated the individual MET h/week from questionnaire data (based on the VITAL study questionnaire, FHCRC, Seattle). Spearman correlation analysis was used to assess the relationship between abdominal fat distribution, Vit D levels (adjusted for season), and METs. Moreover, subgroup analyses in male subjects were performed whereas sample size was too small for further subgrouping. Results: Study participants were on average 62 years old and diagnosed with either colon (44%), rectal (50%) or rectosigmoid (6%) primary cancer. Data were available on n=186 (BMI), n=118 (CT scans), n=133 (Vit D) and n=96 (MET) subjects based on sequential implementation of assessments. Only correlations with at least 40 individuals are reported. Our evaluation suggests a negative association between Vit D and VFA (r=-0.14, p=0.20). However, no association was found for BMI with Vit D and MET levels, respectively. MET levels were negatively correlated with VFA/SFA ratio (r=-0.22, p=0.13). In male patients MET levels were positively correlated with SFA (r=0.27, p=0.08) and negatively correlated with VFA/SFA ratio (r=-0.41, p<0.01). Conclusion: Our pilot data suggest that an increased portion of visceral but not subcutaneous fat may be linked to lower levels of Vit D. Furthermore, higher MET levels may be associated with a higher visceral/subcutaneous fat ratio and might influence Vit D levels by changes in abdominal fat distribution. Additional data collection is underway and will be presented. Citation Format: Jürgen Staffa, Johanna Welzel, Katharina Buck, Hanna Högenauer, Petra Schrotz-King, Nina Habermann, Dominique Scherer, Stephanie Tosic, Verena Widmer, Clare Abbenhardt, Gerd Würtele, Robert Owen, Michael Hoffmeister, Hermann Brenner, Jenny Chang-Claude, Hans-U. Kauczor, Cornelia M. Ulrich. The relationship between abdominal fat distribution, vitamin D levels, and physical activity in colorectal cancer patients: A pilot study. [abstract]. In: Proceedings of the AACR Special Conference on Post-GWAS Horizons in Molecular Epidemiology: Digging Deeper into the Environment; 2012 Nov 11-14; Hollywood, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(11 Suppl):Abstract nr 79.