Diabetes Risk Tied to Breast Cancer Hormone Therapy

Exploring the possible complications of tamoxifen and aromatase inhibitors

Health Writer

Breast cancer treatments are known to have a range of possible adverse health outcomes, even as they save or extend lives. Radiation therapy can cause dryness, itching and blistering of skin, and overall fatigue. Chemotherapy can cause loss of hair, depressed immune function, nausea, and vomiting. In fact, there are limits to certain chemotherapy drug regimens because of the risk of cardiotoxicity. “Chemo brain” is a term associated with memory loss and cognitive function impairment during and after chemotherapy treatment.

Other long term and late side effects from breast cancer therapies can include: headaches, dental issues, lymphedema, bone loss, osteoporosis, cataracts, blood clots, menopausal symptoms, sexual difficulties, and infertility. Younger cancer survivors, especially, should discuss issues like bone health and menopausal symptoms. However, diabetes complications could be added to the list. A May 2018 study published in the Journal of Clinical Oncology sheds some light on the higher risk of diabetes in breast cancer survivors who receive hormone therapy.

When women are diagnosed with hormone-receptor positive breast cancer, they are often treated with Tamoxifen or an aromatase inhibitor (AI) to prevent recurrence of the cancer. The study suggests that one of the lingering health outcomes may be an increased risk of diabetes in these breast cancer survivors. The study looked at 2,246 female breast cancer patients who did not have diabetes at the time of their diagnosis, and who also did not have diabetes in the first year after diagnosis and treatment.

The Israeli researchers found that the two types of hormone therapy increased risk of diabetes occurring in these women later on, by two and half times the rate found in women who did not receive the hormone therapy. Out of the entire test group, 324 women developed diabetes. The risk persisted during the entire therapeutic treatment with the hormone therapy. The research team also highlighted that the diabetes could have possibly been avoided by not using the hormone therapy.

The researchers did, however, make it clear that breast cancer survivors who match to this therapy should not be denied therapy because of the diabetes risk. The survival benefits far outweigh the diabetes risk.Still they point to the small window during which hormone therapy was used and the dramatic uptick in the diabetes risk. Taking an AI had a higher risk of diabetes compared to Tamoxifen.

It’s important to note that individuals who died during therapy were not included. If they developed diabetes prior to their death, they were not included in the data. Researchers note that the prevalence of diabetes in the population of breast cancer survivors analyzed in the study increased from 6 percent in 2002 to 28 percent in 2015.

The researchers also looked at a subset of the larger group, 570 patients, that included women with diabetes who were alive for the duration of the study. The average time it took these women on hormone therapy to develop diabetes was 6.4 years. The women who did develop diabetes seemed to have had more outpatient visits, were exposed to more drugs known to promote diabetes, and received longer periods of hormone therapy compared to women who did not develop diabetes over the course of follow up.

In fact, following a diagnosis of diabetes, the same smaller group of women were observed to have a higher rate of obesity, were more likely to be consuming an unhealthy diet, and were less likely to exercise, which are all risk factors for diabetes. One theory that considers the association of obesity with diabetes, suggests that these women were already predisposed or primed to develop diabetes, independent of the hormone therapy they received. It’s important to remember that some of the other treatments for breast cancer – surgery, debilitating chemotherapy – can make someone so tired that they are sitting a lot, eating a lot, sleeping a lot and therefore prone to weight gain, obesity, and possibly diabetes.

The researchers concluded that it’s crucial to take all these variables into account so that the risk of diabetes can be minimized, whether caused by lifestyle factors, duration of hormone therapy, or the two combined. If you are diagnosed with breast cancer, then optimizing your lifestyle, as much as possible, may help you to battle the disease and limit the risk of diabetes.

Some quick lifestyle tips to help to limit excessive weight gain or to possibly intercept any diabetes risk associated with hormone therapy:

  • Request a consultation or referral to a dietician or nutritionist to discuss best eating practices for your diagnosis and treatment and to avoid excessive weight gain or weight loss.
  • Begin an exercise program which should be sustained during and after treatment. Consider devising a program with an experienced personal trainer or physical therapist. They can periodically modify the program based on any issues you’re having.
  • Avoid the “dirty dozen” – a list of fruits and vegetables whose skins may have pesticide load. Learn about the “clean 15.”
  • Consider following the Mediterranean-style of eating, with portion control, which is considered to be a heart healthy and bone supportive diet.
  • Specifically avoid unhealthy saturated and trans fats and highly processed grain foods, and limit meat consumption.
  • Meet daily sleep goals, since diminished sleep can provoke weight gain and possibly undermine immune function.
  • Use de-stressing techniques so you avoid stress-eating.