Coffee consumption modifies risk of breast cancer

[NEWS, 11 May 2011] In a new study, published in the journal Breast Cancer Research, a research group at Karolinska Institutet shows that drinking coffee may reduce the risk of so called ER-negative breast cancer in women.

The researchers compared lifestyle factors and coffee consumption between women with breast cancer and healthy age-matched women. They found that coffee drinkers had a lower incidence of breast cancer than women who rarely drank coffee. Furthermore, after adjusting the collected data to account for other influencing factors, such as menopause, exercise, weight, education and family history of breast cancer, the researchers found that the protective effect of coffee on breast cancer was only measurable for so called estrogen-receptor (ER)-negative breast cancer.

Breast cancer is a heterogeneous disease and can be characterized on the basis of estrogen receptor (ER) expression in the tumour cells. ER-positive cancers are, in contrast to ER-negative cancers, dependant on estrogen for their growth. The two breast cancer subtypes are generally considered as biologically distinct diseases and have been associated with remarkably different gene expression profiles. ER status is important clinically, and is used both as a prognostic indicator and treatment predictor. The ER-positive cancers are more prevalent in older age groups and are normally treated with anti hormonal therapy, such as tamoxifen.

According to Dr Jingmei Li, who led the study at the Department of Medical Epidemiology and Biostatistics, there is often conflicting information about the beneficial effects of coffee on the human body, as different study results contradict each other. However, when the current study was compared with the results of a similar German study, it was discovered that the German data showed the same trend but with a much weaker relationship between coffee consumption and ER-negative breast cancer.

"We suggest that this may have something to do with the way the coffee was prepared, or the type of bean preferred", says Jingmei Li. "We can not say which mechanism lies behind the beneficial effect of coffee yet. It is unlikely that the protective effect is due to phytoestrogens present in coffee since there was no reduction in the incidence of ER-positive cancer, that is, hormone dependent cancer, in this study."

Approximately one third of all breast cancers are ER-negative, and cancers of this ER subtype are highly age dependent and generally have a more aggressive clinical course than hormone receptor-positive disease.

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