PPT:The PPT was a randomized, controlled trial being carried out at eight Clinical Centers in the United States. The dietary goals for the intervention arm were 20% of calories from fat, 18g fiber/1000 kcal, and 5-8 servings of fruits and vegetables (the exact number based on caloric intake). Three different dietary assessment instruments were used in the PPT: a modified Block/NCI Food Frequency Questionnaire (FFQ), Four Day Food Records (4DFR), and 24 Hour Recalls. Participants underwent colonoscopy again at baseline and at one (T1) and four (T4) years into the study. Blood specimens were collected on all participants annually. Recruitment went on from 1991-4. A total of 38,277 potential participants were screened at the eight Clinical Centers. Of these, 2079 were randomized into the study, with 1037 in the intervention and 1042 in the control group. The mean age of PPT participants at baseline was 61.5 years. 35% of participants are women, 10% minority. T4 colonoscopic endpoint assessment and active intervention were completed in early April, 1998. A report of the main study findings was published in 2000. years ago (New Engl J Med 2000;342:1149-55). Additional manuscripts have been published, submitted, or are in preparation. The Continued Follow-up Study should has now been completed;a report is now in press.CONCeRN:Asymptomatic women were referred for colorectal screening to one of three regional military medical centers, including Bethesda Naval Hospital, from 1999 to 2002. Blood and tissue samples were collected as well as general health information, along with a detailed risk factor questionnaire. Dietary and biospecimen analyses are currently underway using data from the etiologic component of the study. These include an investigation of meat and meat-mutagens and the risk of colorectal adenoma as well as a study of genomic methylation of leukocyte DNA and colorectal adenoma risk, and modification by dietary folate.
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