In recent years, several studies have examined the link between diabetes and various types of cancer. Most of them have focused on the cancer risk faced by people with diabetes — not the diabetes risk faced by cancer survivors. One recent study found that for people with type 2 diabetes and obesity, undergoing bariatric (weight-loss) surgery and experiencing diabetes remission were linked to a lower overall cancer risk in the following years. Another study found that having diabetes may modestly increase the risk for blood cancers like leukemia and lymphoma. And when it comes to diabetes treatments, a recent study found that people with diabetes who take a GLP-1 agonist to help control their blood glucose are no more likely to develop breast cancer.
For the latest study, researchers looked at how having breast cancer — and undergoing certain treatments for that cancer — were linked to the risk for developing diabetes, high blood pressure, or abnormal blood lipid (cholesterol and triglyceride) levels. They used data from 14,942 women diagnosed with invasive breast cancer between 2005 and 2013, and compared their outcomes with those of 74,702 matched controls — women who shared the same birth year and race or ethnicity, but didn’t have breast cancer. As the numbers indicate, there were five matched controls for every breast cancer survivor in the study. The average age of all participants was 61, and 65% of participants identified as non-Hispanic white.
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Breast cancer survivors modestly more likely to develop diabetes
Compared with matched controls, women who survived breast cancer were modestly more likely to develop diabetes after two years, with a diagnosis rate of 2.1% compared with 1.7%. After 10 years, they were also still modestly more likely to develop diabetes, with a diagnosis rate of 9.3% compared with 8.8%. After adjusting for several factors that can influence the risk for diabetes — including body-mass index (BMI, a measure of weight that takes height into account) and cardiovascular issues — breast cancer survivors were found to be 16% more likely than matched controls to develop diabetes over the course of 10 years. This relative risk was slightly higher for women who underwent certain forms of breast cancer treatment — 23% for those who had chemotherapy, 29% for those who had left-sided radiation, and 23% for those who received endocrine therapy.
When it came to the risk for high blood pressure, cancer survivors were more likely to have it after two years — at a rate of 10.9% compared with 8.9% for matched controls. Compared with matched controls, the risk for high blood pressure was 11% higher in women who underwent left-sided radiation and 10% higher in those who received endocrine therapy. Both overall and within subsets of women who underwent specific breast cancer treatments, the relative risk for both diabetes and high blood pressure — compared with similar matched controls — was higher in those with a normal BMI, or less than 25. In other words, women with a normal body weight saw a larger increase in the risk for diabetes and high blood pressure if they had breast cancer, compared with the increase seen in overweight or obese women if they had breast cancer.
These findings may help guide breast cancer survivors and their health care providers in deciding how to manage risk factors for diabetes and high blood pressure, such as dietary choices and physical activity. Future studies, the researchers wrote, should examine different strategies for managing the risk for diabetes and cardiovascular problems in breast cancer survivors.
Want to learn more about diabetes and breast cancer? Read “No Increased Breast Cancer Risk Found With GLP-1 Agonists” and “Aspirin, Breast Cancer, and Type 2 Diabetes.”