Coffee consumption and risk of renal cell carcinoma.

BACKGROUND: Studies have suggested an inverse association between coffee consumption and risk of renal cell carcinoma (RCC); however, data regarding decaffeinated coffee are limited. METHODS: We conducted a case-control study of 669 incident RCC cases and 1,001 frequency-matched controls. Participants completed identical risk factor questionnaires that solicited information about usual coffee consumption habits. The study participants were categorized as non-coffee, caffeinated coffee, decaffeinated coffee, or both caffeinated and decaffeinated coffee drinkers. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using logistic regression, adjusting for multiple risk factors for RCC. RESULTS: Compared with no coffee consumption, we found an inverse association between caffeinated coffee consumption and RCC risk (OR 0.74; 95% CI 0.57-0.99), whereas we observed a trend toward increased risk of RCC for consumption of decaffeinated coffee (OR 1.47; 95% CI 0.98-2.19). Decaffeinated coffee consumption was associated also with increased risk of the clear cell RCC (ccRCC) subtype, particularly the aggressive form of ccRCC (OR 1.80; 95% CI 1.01-3.22). CONCLUSIONS: Consumption of caffeinated coffee is associated with reduced risk of RCC, while decaffeinated coffee consumption is associated with an increase in risk of aggressive ccRCC. Further inquiry is warranted in large prospective studies and should include assessment of dose-response associations.