Case-control analysis of pyramid food groups and bladder cancer risk

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We analyzed the association between U.S. Department of Agriculture (USDA) pyramid food groups and BC risk using data collected in a large case-control study. The study included 884 histologically confirmed BC cases and 926 healthy controls matched to cases by age (± 5 years), gender and ethnicity. Epidemiologic and dietary data were collected using structured questionnaires via an in-person interview. Dietary intake was reported on the National Cancer Institute- Block 135-item food frequency questionnaire (FFQ). Foods were categorized into the MyPyramid food groups as defined by the 2006 USDA Pyramid database. Unconditional logistic regression was used to estimate odds ratios (ORs) and the 95% confidence intervals (95% CI) after adjustment for age, gender, ethnicity, smoking status, pack years of smoking and total energy intake. Classification and Regression Tree (CART) analysis was used to identify important food groups associated with BC risk. Significant inverse associations were observed for total vegetable, cruciferous vegetable, and orange vegetable intakes and BC risk. Compared to those in the lowest quartile of total vegetable intake, the ORs for the second, third and fourth quartiles of total vegetable intake were 0.81 (95% CI: 0.62-1.07), 0.71 (95% CI: 0.54-0.92), and 0.67 (0.50-0.90), respectively (P-for trend =0.005). Compared to those in the lowest quartile, those in the highest quartile of cruciferous vegetable intake had an OR=0.69 (95% CI: 0.52-0.92) (P-for trend= 0.001) and those in the highest quartile of orange vegetable intake had OR=0.66 (95% CI: 0.51-0.91) (P-for trend=0.003). Vegetables individually associated with decreased BC risk were broccoli, raw spinach, green cabbage, coleslaw, sauerkraut, carrots, and salads made with lettuce. No association was observed for total fruits or citrus fruits. Higher intake of red meat was associated with increased BC risk with ORs of 1.11 (95% CI: 0.83-1.49), 1.47 (95% CI: 1.10-1.96) and 1.67 (95% CI: 1.22-2.27) for the 2^nd, 3^rd and 4^th quartile, respectively, as compared to the lowest quartile of intake (P-for trend<0.001). Higher intakes of beef steaks, pork chops and bacon were each associated with increased BC risk in a dose-response pattern. CART analyses yielded 12 terminal nodes identifying a range of high and low risk subgroups with the ORs for terminal nodes ranging from 0.95 to 5.97, indicating that multiple food groups jointly modified BC risk. The major food groups in the tree structure of the CART analysis were cruciferous vegetables, red meat, added sugar, orange vegetables, cheese, and fruit other than citrus fruits. Our data strongly support that high cruciferous vegetable and orange vegetable consumption may protect against BC, while subjects with high consumption of red meats may be at increased risk. Our study also stresses the importance to jointly assess the role of multiple food groups in modifying BC risk. Supported by the NCI grants CA 74880 and CA 91846.