Objective: The available epidemiological evidence indicates that drinking alcohol per se is associated with breast cancer. However, it has not been investigated how the breast cancer risk for a given total alcohol consumption depends on the drinking frequency.

Methods: Within the prospective study on 'Diet, Cancer and Health', we examined the relationship between breast cancer, intake of total alcohol and frequency of drinking among 23,778 postmenopausal women, among whom 425 cases of breast cancer accrued during a median follow-up of 4.8 years.

Results: The dose-response relationship between total alcohol intake and breast cancer showed an increase in the rate ratio of 1.10 per 10 g/day (95% CI: 1.04-1.16) with no evidence for differences by type of alcohol beverage. No interaction was found between drinking frequency and total alcohol intake in the risk of breast cancer (p = 0.40).

Conclusions: The present study supports previous ones in showing a monotonic increase in the risk of breast cancer among postmenopausal women with increasing average daily intake of alcohol, and this relationship with alcohol intake did not depend on drinking frequency.