Background: Alcohol consumption increases breast cancer risk. Some studies suggested that this association is stronger or limited to tumors expressing estrogen receptors (ER).
Methods: We investigated the role of alcohol according to ER and progesterone receptor (PR) status in a case-control study on breast cancer conducted from 1991 to 1994 in three Italian areas. Cases were 989 women with incident, histologically confirmed breast cancer. Controls were 1,350 women admitted to hospitals in the same catchment areas for acute nonneoplastic diseases. A validated food-frequency questionnaire was used to collect information on dietary habits and lifetime consumption of various alcoholic beverages. Multiple logistic regression models were used to estimate odds ratios and 95% confidence interval (95% CI).
Results: Alcohol drinking was associated with ER+ tumors (odds ratio, 2.16; 95% CI, 1.68-2.76 for an intake of > or =13.8 g/d as compared with nondrinkers). The odds ratio was 1.13 (95% CI, 1.07-1.20) for a 10-g increase in daily intake. For ER- tumors, the relation with alcohol consumption was not significant (odds ratio, 1.36; 95% CI, 0.93-2.01). When breast cancers were further classified according to PR, the findings for ER+PR+ cancers were similar to those for all ER+ ones, with an odds ratio of 2.34 (95% CI, 1.81-3.04) for an intake of > or =13.8 g/d. No significant association emerged for ER-PR- tumors (odds ratio, 1.25; 95% CI, 0.81-1.94).
Conclusion: This study supports the hypothesis that alcohol is more strongly related to ER+ than to ER- breast tumors.