Coffee, tea, caffeine intake, and the risk of cancer in the PLCO cohort

Background: The association between coffee intake, tea intake and cancer has been extensively studied, but associations are not established for many cancers. Previous studies are not consistent on whether caffeine may be the source of possible associations between coffee and cancer risk. Methods: In the Prostate, Lung, Colorectal, and Ovarian cancer screening trial, of the 97 334 eligible individuals, 10 399 developed cancer. Cancers included were 145 head and neck, 99 oesophageal, 136 stomach, 1137 lung, 1703 breast, 257 endometrial, 162 ovarian, 3037 prostate, 318 kidney, 398 bladder, 103 gliomas, and 106 thyroid. Results: Mean coffee intake was higher in lower education groups, among current smokers, among heavier and longer duration smokers, and among heavier alcohol drinkers. Coffee intake was not associated with the risk of all cancers combined (RR = 1.00, 95% confidence interval (CI) = 0.96-1.05), whereas tea drinking was associated with a decreased risk of cancer overall (RR = 0.95, 95% CI = 0.94-0.96 for 1 + cups per day vs <1 cup per day). For endometrial cancer, a decreased risk was observed for coffee intake (RR = 0.69, 95% CI = 0,52-0.91 for >= 2 cups per day). Caffeine intake was not associated with cancer risk in a dose-response manner. Conclusions: We observed a decreased risk of endometrial cancer for coffee intake, and a decreased risk of cancer overall with tea intake.