Coffee and black tea consumption and breast cancer mortality in a cohort of Swedish women

BACKGROUND: Coffee and black tea contain a mixture of compounds that have the potential to influence breast cancer risk and survival. However, epidemiologic data on the relation between coffee and black tea consumption and breast cancer survival are sparse. METHODS: We investigated the association between coffee and black tea consumption and survival among 3243 women with invasive breast cancer in the Swedish Mammography Cohort. Intake was estimated using a food frequency questionnaire. Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% confidence intervals (95% CIs). RESULTS: From 1987 to 2010 there were 394 breast cancer-specific deaths and 973 total deaths. Coffee and black tea were not associated with breast cancer-specific or overall mortality. Women consuming 4+ cups of coffee per day had a covariate and clinical characteristics-adjusted HR (95% CI) of death from breast cancer of 1.14 (0.71–1.83; p(trend)=0.81) compared with those consuming <1 cup per day. Women consuming 2+ cups of black tea per day had a covariate and clinical characteristics-adjusted HR (95% CI) of death from breast cancer of 1.02 (0.67–1.55; p(trend)=0.94) compared with non-tea drinkers. Caffeine was also not associated with breast cancer-specific (HR for top to bottom quartile=1.06; 95% CI=0.79–1.44; p(trend)=0.71) or overall mortality. CONCLUSION: Our findings suggest that coffee, black tea, and caffeine consumption before breast cancer diagnosis do not influence breast cancer-specific and overall survival.