In June 2018 researchers from the USA published the results of their study to assess the association of coffee consumption with post-menopausal breast cancer risk, including by status of post-menopausal hormone therapy (hormone replacement therapy). A total of 126,182 post-menopausal women (2,636 with breast cancer, 123,546 with no history of breast cancer) from the UK were included in the study. Information on breast cancer risk factors and coffee consumption was collected at the start of the study and updated during follow-up. Results showed that coffee consumption did not appear to be associated with breast cancer risk. Women with no history of post-menopausal hormone treatment who consumed 4+ cups of coffee per day appeared to have a 16% reduced risk of breast cancer when compared to women who consumed up to 7 cups of coffee per week. However, in women who had taken post-menopausal hormone treatment, consuming 4+ cups/day appeared to have a 22% increased risk of breast cancer when compared to women consuming up to 7 cups/week. No association was found among current users of post-menopausal hormone treatment.
Yaghjyan L et al. Interactions of coffee consumption and postmenopausal hormone use in relation to breast cancer risk in UK Biobank. Cancer Causes Control. 2018 Jun;29(6):519-525.