The relations between individual foods and nutrients to colorectal tumours are conflicting. Few studies have taken into account the interdependence between individual components of diet and their possible interactions. The aim of the study was to examine the associations between dietary patterns and the risk of colorectal adenoma recurrence in the European fibre-calcium intervention trial. Among the 640 patients with confirmed adenomas at the index colonoscopy, 592 had an initial dietary assessment using a diet history questionnaire. The present analysis was restricted to 277 men and 165 women without history of adenoma prior to the index colonoscopy and who completed the study. The main end point was the 3-year recurrence of adenomas. Principal component analysis was used to identify dietary patterns from 50 food groups. Ninety-two patients presented new colorectal adenomas at the 3-year colonoscopy (65 men and 27 women). In men, three meaningful dietary patterns emerged from analysis, explaining 21.3% of variability. They were called 'Mediterranean', 'Sweets and snacks' and 'High fat and proteins' patterns. None of them were significantly related to the overall recurrence of colorectal adenomas either in univariate or multivariate analyses. Among women, the 'Mediterranean', the 'Western' and the 'Snacks' patterns explained 21.9% of variability. The 'Mediterranean' pattern characterized by a high consumption of olive oil, vegetables, fruit, fish and lean meat significantly reduced adenoma recurrence [second tertile: adjusted odds ratio (OR)=0.50, 95% confidence interval (CI)=0.18-1.42; third tertile: adjusted OR=0.30, 95% CI=0.09-0.98; P for linear trend=0.04]. The 'Western' and 'Snacks' patterns were not associated with recurrence among women. In conclusion, this study suggests that the Mediterranean dietary pattern may reduce the recurrence of colorectal adenomas, at least in women. These exploratory results need to be confirmed by larger studies.

ABSTRACT. Some studies of polymorphisms in prostate cancer (PCa) analyze individuals in a uniform manner, regardless of genetic ancestry. However, PCa aggressiveness differs between subjects of African descent and those of European extraction. Thus, genetic ancestry analysis may be used to detect population stratification in case-control association studies. We genotyped 11 ancestry informative markers to estimate the contributions of African, European, and Amerindian ancestries in a case-control sample of 213 individuals from Bahia State, Northeast Brazil, including 104 PCa patients. We compared this data with self-reported ancestry and the stratification of cases by PCa aggressiveness according to Gleason score. A larger African genetic contribution (44%) was detected among cases, and a greater European contribution (61%) among controls. Self-declaration data revealed that 74% of PCa patients considered themselves non-white (black and brown), and 41.3% of controls viewed themselves as white. Our data showed a higher degree of European ancestry among fast-growing cancer cases than those of intermediate and slow development. This differs from many previous studies, in which the prevalence of African ancestry has been reported for all grades. Differences were observed between degrees of PCa aggressiveness in terms of genetic ancestry. In particular, the greater European contribution among patients with highgrade PCa indicates that a population's genetic structure can influence case-control studies. This investigation contributes to our understanding of the genetic basis of tumor aggressiveness among groups of different genetic ancestries, especially admixed populations, and has significant implications for the assessment of inter-population heterogeneity in drug treatment effects.