We evaluated the association between
caffeine consumption and
breast cancer risk in women enrolled in a completed
cancer prevention trial. Detailed dietary information was obtained at baseline (1992-1995) from 38 432 women 45 years or older and free of
cancer. During a mean follow-up of 10 years, we identified 1188 invasive
breast cancer cases.
RESULTS: Consumption of
caffeine and caffeinated beverages and foods was not statistically significantly associated with overall risk of
breast cancer. The multivariate relative risks (RRs) of
breast cancer were 1.02 (95% confidence interval [CI], 0.84-1.22) for
caffeine (top vs bottom quintile), 1.08 (0.89-1.30) for
coffee (> or =4 cups daily vs almost never), and 1.03 (0.85-1.25) for
tea (> or =2 cups daily vs almost never). However, in women with benign
breast disease, a borderline significant positive association with
breast cancer risk was observed for the highest quintile of
caffeine consumption (RR, 1.32; 95% CI, 0.99-1.76) and for the highest category of
coffee consumption (> or =4 cups daily) (1.35; 1.01-1.80); tests for interaction were marginally significant.
Caffeine consumption was also significantly positively associated with risk of
estrogen receptor-negative and
progesterone receptor-negative
breast cancer (RR, 1.68; 95% CI, 1.01-2.81) and
breast tumors larger than 2 cm (1.79; 1.18-2.72).
CONCLUSIONS: