In an ongoing screening colonoscopy-based cross-sectional study, known as the Case Transdisciplinary Research in Cancer and Energetics [TREC] Colon Polyps Study, we have prospectively collected data (lifestyle risk factors and fasting blood samples) from 1,259 individuals from January 2006 to March 2009. Patients were recruited from University Hospitals Case Medical Center and affiliated endoscopy centers and were eligible if they were scheduled for a routine screening colonoscopy; informed consent was obtained from each subject prior to their participation in the study. Individuals were determined to be ineligible if they had a prior diagnosis of cancer, colon polyps or inflammatory bowel disease (including Crohn’s disease or ulcerative colitis), or were under the age of 30. After signing the informed consent, each participant was asked to complete a phone survey, fill out questionnaires and donate a blood sample. The phone survey was based on the lifestyle risk factor questionnaire (RFQ) developed by the NCI colon cancer family registry group (http://epi.grants.cancer.gov/CFR/about_questionnaires.html). The questionnaires each participant filled out included the Arizona Food Frequency Questionnaire, Physical Activity and Meat Preparation questionnaire. All three questionnaires were developed and validated by the Arizona Diet, Behavior and Quality of Life Assessment Center (http://azcc.arizona.edu/research/shared-services/bmss). A research nurse obtained the blood sample just prior to their colonoscopy and immediately refrigerated it. Blood processing was done the same day as collection. All tubes were spun for 15 minutes at 600g and aliquots of plasma, serum and concentrated buffy coat were prepared and frozen at −80°C. Incident cases were defined by histological confirmation of adenomatous polyps after their colonoscopy. We excluded individuals diagnosed with cancer. Patients who had a negative colonoscopy were classified as controls. The response rate was 64.9% among individuals eligible to participate in the study. The distribution of age, gender and race did not differ between individuals who participated and those who elected not to participate (p>0.05). This study has been approved by the University Hospitals Case Medical Center Institutional Review Board.
From these 1,259 participants who completed all the study procedures by the time of this analysis, 1 was excluded because of rectal cancer diagnosis. From these remaining 1,258, 2 were excluded because they were missing info on history of diabetes, 3 were missing information on diabetes medication use in the past 2 years and 31 had unreadable values of insulin/glucose. Thus, the final study population for this analysis included 1,222 individuals; 902 without adenomas (73.8%) and 320 with adenomas (26.2%).