Diabetes and breast cancer

If life were fair, no one would be diagnosed with a second chronic or serious disease after already being diagnosed with breast cancer. If life were fair, the cancer diagnosis would give you a free pass for everything else health-related. Unfortunately, it does not work that way. We are still in the same population pools that we were in before cancer, and, by and large, we have the same risks that we previously carried.

Indeed, for some people, it seems that breast cancer is the tip of the iceberg of health issues, and one thing follows another for a long, long time. Some issues are directly related to cancer treatment, e.g. lymphedema, but most have an unclear association if there indeed is any connection. A number of studies have looked at the possible link between breast cancer and diabetes. Women who have diabetes are known to be at an increased risk of developing breast cancer for at least two reasons: obesity (a risk factor for both) and the high glucose and insulin levels in women who have poorly controlled diabetes. These higher levels may result in some hormonal changes that can increase cancer risk. Note that this risk is not relevant for women whose diabetes is well managed with either diet or medications.

Read about BIDMC's breast cancer program here.

A recent Israeli study came at this question from a different perspective. Instead of starting with diabetes, they wondered whether women who had breast cancer were at a higher risk of developing diabetes. The answer turned out to be yes and to be especially yes for women with ER positive breast cancers who are taking hormonal/anti-estrogen therapies. Younger women taking tamoxifen had a 2.2% greater risk of developing breast cancer, while post-menopausal women taking one of the AIs had a 4.3% higher risk. This strong result was startling.

What does this mean for us and what can we do to try to protect ourselves from additional health worries? No one is suggesting that women with ER positive breast cancers should avoid these medications. The hormonal treatments are extremely powerful and reduce recurrence risk, on average, by 50%. These results do mean that we need to pay attention to our diets and exercise and other so-called lifestyle factors that may increase or decrease our risk of a range of things. I know that I have written often about the importance of maintaining a healthy weight and sticking with a mild to moderate regular exercise program; it bears repeating because it is really important.

By complying with the recommended treatment for breast cancer and going through surgery, radiation, chemotherapy, and/or hormonal therapy, we have done the most important things. It is smart to try to increase the margins, to work the edges, to give ourselves the best possible chance of staying well and living long and healthy lives.

If, because of your personal or family history, you know that you are at high risk of diabetes, it probably would be wise to consult with an endocrinologist.