Treatment for diabetes can affect the density of breast tissue, possibly impacting on the risk of breast cancer, a European conference will hear today.
Dr Zorana Jovanovic Andersen and colleagues at the University of Southern Denmark, Esjberg, Denmark, looked at the effect of diabetes treatments such as insulin and metformin on "mammographic density". This is among the strongest risk factors for breast cancer, they explain.
At a conference in Amsterdam, the Netherlands, today (9 March), the team present their study, the first to look at the possible breast cancer risks of various diabetes treatments.
They carried out a study of 5,644 women who had a mammogram between 1993 and 2001. Participants had an average age of 56 years. A small proportion – 2.4% – had diabetes. These women "were less likely to have mixed or dense breasts, as opposed to fatty ones, both before and after adjustment for other factors such as being overweight," the team say.
Taking insulin appeared to increase mammographic density, whereas the drug metformin reduced it.
The researchers report: "Diabetes is associated with an increased risk of breast cancer, but the exact mechanisms which bring this about are still unclear. We know that insulin is an important growth factor for all body tissues, and even if we do not know exactly how it affects the development of cancer cells, it is also highly plausible that it increases breast density."
Next, the team plan to follow up the women in this study for new cases of breast cancer and observe the effect of a wider range of diabetes treatments on breast cancer risk.
* The conference also heard how a large investigation has revealed new insights into the benefits of physical activity on breast cancer risk.
The study, by Ms Shadi Azam, MSc, of the University of Southern Denmark, Esbjerg, Denmark, and colleagues indicates that the protective effect of physical activity is not due to any link with breast density.
Although the breast cancer risk is higher for women with more dense breasts, those who do more physical activity do not have less dense breasts, they report.
"The protective effect might be through other mechanisms than breast density," the team will report tomorrow (10 March) at a conference in Amsterdam, the Netherlands.
The study included 5,703 pre- and post-menopausal Danish women who underwent breast screening between 1991 and 2001. Number of hours of physical activity per week were recorded for each woman.
Ms Azam says: "We know that breast density is one of the strongest risk factors for breast cancer risk. Women with high density breasts – more than 75% mammographic density – have a four to six times’ higher risk of developing the disease than do those women with a breast density of lower than 25%."
This is because it makes mammograms harder to interpret, and because breast density can lead to an increased risk of most of cellular abnormalities that can lead to breast cancer.
"The ability to link these breast density data to such a large group of women and information on their leisure-time, transport, and occupational-related physical activity is unique to Denmark," Ms Azam adds.
"We initially found a significant association between participation in sports and cycling with the chances of having denser breasts, but the odds of having dense breasts were reduced and did not reach a significant level after we adjusted for other factors."
Poster number 158, "Diabetes, diabetes treatment and mammographic density in Danish diet, cancer, and health cohort" presented on Wednesday 9 March at the 10th European Breast Cancer Conference, Amsterdam, the Netherlands.
Abstract no: 13. "The association of physical activity with mammographic density: A register-based cohort study" presented on Thursday 10 March at the 10th European Breast Cancer Conference, Amsterdam, the Netherlands.
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