The Polyp Prevention Trial–Continued Follow-up Study: No Effect of a Low-Fat, High-Fiber, High-Fruit, and -Vegetable Diet on Adenoma Recurrence Eight Years after Randomization

Abstract

The Polyp Prevention Trial (PPT) was a multicenter randomized clinical trial to evaluate the effects of a highfiber (18 g/1,000 kcal), high-fruit and -vegetable (3.5 servings/1,000 kcal), and low-fat (20% of total energy) diet on the recurrence of adenomatous polyps in the large bowel over a period of 4 years. Although intervention participants reported a significantly reduced intake of dietary fat, and increased fiber, fruit, and vegetable intakes, their risk of recurrent adenomas was not significantly different from that of the controls. Since the PPT intervention lasted only 4 years, it is possible that participants need to be followed for a longer period of time before treatment differences in adenoma recurrence emerge, particularly if diet affects early events in the neoplastic process. The PPTContinued Follow-up Study (PPT-CFS) was a postintervention observation of PPT participants for an additional 4 years from the completion of the trial. Of the 1,905 PPT participants, 1,192 consented to participate in the PPT-CFS and confirmed colonoscopy reports were obtained on 801 participants. The mean time between the main trial end point colonoscopy and the first colonoscopy in the PPT-CFS was 3.94 years (intervention group) and 3.87 years (control group). The baseline characteristics of 405 intervention participants and 396 control participants in the PPT-CFS were quite similar.Even though the intervention group participants increased their fat intake and decreased their intakes of fiber, fruits, and vegetables during the PPT-CFS, they did not go back to their prerandomization baseline diet (P < 0.001 from paired t tests) and intake for each of the three dietary goals was still significantly different from that in the controls during the PPT-CFS (P < 0.001 from t tests). As the CFS participants are a subset of the people in the PPT study, the nonparticipants might not be missing completely at random. Therefore, a multiple imputation method was used to adjust for potential selection bias. The relative risk (95% confidence intervals) of recurrent adenoma in the intervention group compared with the control group was 0.98 (0.88-1.09). There were no significant intervention-control group differences in the relative risk for recurrence of an advanced adenoma (1.06; 0.81-1.39) or multiple adenomas (0.92; 0.77-1.10). We also used a multiple imputation method to examine the cumulative recurrence of adenomas through the end of the PPT-CFS: the intervention-control relative risk (95% confidence intervals) for any adenoma recurrence was 1.04 (0.98-1.09). This study failed to show any effect of a low-fat, high-fiber, high-fruit and -vegetable eating pattern on adenoma recurrence even with 8 years of follow-up. (Cancer Epidemiol Biomarkers Prev 2007;16(9):1745 -52)

Obesity and Colorectal Cancer

“…Similarly, the Polyp Prevention Trial (PPT) on Dietary Intervention carried out to evaluate the effect of a highfiber, high fruit and vegetables and low fat diet on recurrence of adenomatous polyps did not reveal any protective effect 20 . The PPT study failed to show any effect of a low fat, high fibre, high fruit and vegetables eating pattern on adenoma recurrence even with 8 years of follow-up, where as the high intake of fish was found to be associated with lower risk of adenoma recurrence 21 .…”

S3-Leitlinie – Kolorektales Karzinom

“…In Originalpublikationen der letzten Jahre wurde wiederholt eine Assoziation zwischen Ernährungsfaktoren und der Ausbildung eines KRK beobachtet, die mit einer Evidenzstärke zwischen 2b und 4 zu bewerten sind [28 -31]. Allerdings gibt es auch Studien, in denen keine Korrelation zwischen Ernährungsfaktoren und KRK beobachtet wurde [32,33]. Dabei handelt es sich um Assoziationen, nicht um Interventionsstudien.…”

S3-Leitlinie Kolorektales Karzinom Version 1.0 - Juni 2013 AWMF-Registernummer: 021/007OL

“…In Originalpublikationen der letzten Jahre wurde wiederholt eine Assoziation zwischen Ernährungsfaktoren und der Ausbildung eines KRK beobachtet, die mit einer Evidenzstärke zwischen 2b und 4 zu bewerten sind [27 -30]. Allerdings gibt es auch Studien, in denen keine Korrelation zwischen Ernährungsfaktoren und KRK beobachtet wurde [31,32]. Dabei handelt es sich um Assoziationen, nicht um Interventionsstudien.…”