The Link Between Diabetes and Breast Cancer

Which Came First?

It is distressing to consider the possibilities of being diagnosed with a second chronic or scary illness once you have been already diagnosed with breast cancer. It seems as though we ought to get a free pass. You know: the serious illness box has been checked and we can go on to the next thing.

Sadly, that does not turn out to be true. Indeed, for some of us, it can seem as though breast cancer is only the beginning of a myriad of health issues. Some are directly related to the cancer treatment, but others have a much less clear association. A number of studies have looked at the possible link between diabetes and breast cancer. Women who have diabetes are at a higher risk of developing breast cancer for at least two reasons: obesity (a risk factor for both) and high glucose and insulin levels in women who have poorly controlled diabetes. These higher levels may lead to some hormonal changes that can increase breast cancer risk. Learn more about BIDMC's breast cancer program here.

A recent Israeli study came at this from the opposite direction: Are women with breast cancer at a higher risk of developing diabetes? The startling answer turns out to be yes, and yes especially for women who are taking hormonal therapy. Steady yourself here: They found that women taking tamoxifen had a 2.2% greater risk than others of developing diabetes and women taking one of the aromatase inhibitors had a 4.3% higher risk. These numbers were statistically significant.

What does this mean for us other than giving us one more thing to worry about? No one is suggesting that women with estrogen receptor (ER) positive breast cancers should opt out of hormonal therapies. We know that, in general, they reduce the risk of recurrence by about 50% and that is really important. It does mean that we have more reasons to try to take care of ourselves and adopt the habits of healthy living, including regular exercise and weight control. I know that I have written about exercise and weight over and over but they keep coming up as important ways for us to try to exert a little control and stay well.

Women who are at high risk may want to consider a consultation with an endocrinologist. This BreastCancer.org article is worth reading.