Clustering dietary habits and the risk of breast and ovarian cancers

Background: Limited information is available on the relationship between dietary patterns and breast and ovarian cancers. Patients and methods: Cases were 2569 breast cancers and 1031 ovarian cancers hospitalized in four Italian areas from 1991 to 1999. Controls were 3413 women in hospital for acute non-neoplastic diseases. Dietary habits were investigated through a validated food-frequency questionnaire. Dietary patterns were obtained from a K-means clustering on factor scores from factor analysis. Odds ratios (ORs) for both cancers were estimated using unconditional multiple logistic regression models on clusters of patients. Floating absolute risk method was used for reporting 95% floating confidence intervals (FCIs). Results: We identified five groups of subjects. The G3 cluster, including subjects with the lowest intakes of any food group, was used as reference. The G5 cluster, including subjects mainly consuming bread and pasta, was unfavorable for both cancers (OR = 1.23, 95% FCI = 1.08-1.38 for breast cancer, OR = 1.21, 95% FCI = 1.03-1.42 for ovarian cancer). The G1 group, including subjects mainly consuming fruits and vegetables, was protective against ovarian cancer (OR = 0.81, 95% FCI = 0.67-0.98). Conclusions: A diet mainly based on bread and pasta is unfavorable for breast and ovarian cancers; a diet rich in fruits and vegetables may be associated with a reduced risk of ovarian cancer.