Emily is a health communication consultant, writer, and editor at EVR Creative, specializing in public health research and health promotion.
Isabel Casimiro, MD, is board-certified in internal medicine and works as an endocrinologist at the University of Chicago.
Type 2 diabetes increases the risk of breast cancer, but the reason why is not fully understood. It’s thought that a few diabetic factors are at play, including:
This article discusses the connection between diabetes and breast cancer, including the risks of developing breast cancer with diabetes and considerations for how the two conditions can be managed and treated together.
Diabetes is often talked about with diabetes complications like kidney disease and heart disease, so how is it related to breast cancer? While more research is needed to determine a truly causal link between diabetes and breast cancer, studies have shown some diabetes-related factors are at play:
Research suggests that the risk of breast cancer and diabetes is specific to type 2 diabetes and post-menopause. This means post-menopausal people with type 2 diabetes are at higher risk of developing breast cancer. 
When looking at breast cancer prognosis, research has shown that poorer breast cancer prognosis among those with diabetes is due to diabetes-related comorbidities, not diabetes itself. For example, people with obesity, diabetes, and breast cancer may have a worse breast cancer prognosis due to the effects that obesity has on estrogen levels.
Some research has suggested the main reason behind the increased risk of diabetes and breast cancer is body mass index (BMI); however, BMI is associated with both diabetes and breast cancer, which means it can’t be singled out as the main cause of breast cancer among people with diabetes. 
The risk of death from breast cancer and diabetes is affected by various factors, though how significant some factors are in increasing the risk of death is still unclear. For example, one study showed that people with diabetes and breast cancer are at higher risk of death from breast cancer if they’ve had diabetes for a long time and have cardiovascular disease.
One study found that even with the same cancer treatment, Black breast cancer survivors who have diabetes are at increased risk of death from breast cancer. Such racial disparities in breast cancer highlight the need for more research on improving treatment and care for people at increased risk of poor outcomes from breast cancer and diabetes.
Breast cancer treatment and type 2 diabetes treatment take very different approaches. While there are some important medical considerations when treating both conditions, they can be managed at the same time.
People with breast cancer and diabetes can still receive appropriate chemotherapy and radiotherapy like individuals with cancer without diabetes. However, some cancer treatments may have negative effects on diabetes management, which calls for special treatment plans by a healthcare provider
For example, some cancer immunotherapies can prevent insulin production or induce insulin resistance, both of which can cause hyperglycemia. 
In addition, underlying diabetes-related conditions may impact which cancer treatments can be used. Some conditions may limit the kinds of drugs used to treat breast cancer and how many of those drugs can be taken. These conditions include:
For example, radiation increases the risk of cardiovascular complications, which may make it a complex treatment for people with diabetes, heart disease, and breast cancer.
On the other hand, some type 2 diabetes treatments may have some favorable effects on breast cancer outcomes. For example, Glucophage (metformin)—a common medication to control blood sugar—has been found to improve outcomes among people with type 2 diabetes with breast cancer.
Managing diabetes through a healthy diet and physical activity can also have positive impacts on cancer prevention.
Type 2 diabetes and breast cancer share some preventive factors, such as maintaining a healthy weight and being physically active. Some risk factors of breast cancer can’t be changed, such as family history, but others can be. 
Since diabetes-related factors can increase the risk of developing breast cancer, diabetes management is important for preventing breast cancer. Here are three factors that are important for both diabetes management and cancer prevention:
While these lifestyle factors are important for prevention, your health history is unique, and prevention isn’t a one-size fits all approach. It’s best to speak with a healthcare provider if you’re concerned about your risk of breast cancer or diabetes. 
Type 2 diabetes increases the risk of breast cancer among post-menopausal individuals. High blood sugar, high insulin levels, hormonal imbalances, and chronic inflammation are all factors that can increase the risk.
Management of both breast cancer and diabetes requires a thoughtful treatment plan, as some cancer treatments may affect diabetes-related complications.
Lifestyle changes like more exercise, a healthier diet, and limited alcohol intake can help reduce the risk of developing breast cancer with diabetes.
A breast cancer diagnosis can be hard enough to process and deal with without also having to manage life with diabetes.
If you are post-menopausal with diabetes, knowing there may be an increased risk of breast cancer can be scary. While some things are out of your control—such as having a family history of breast cancer or being more at risk because of your race—some risk factors can be changed. Know that you are not alone in this.
There are many others in your shoes who are also trying to figure out how to live with diabetes and breast cancer or prevent it from happening in the first place. We hope this article provides information that empowers you to take control of what you can change and feel more informed when talking with your doctor about managing these conditions.
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Lee KN, Torres MA, Troeschel AN, He J, Gogineni K, McCullough LE. Type 2 diabetes, breast cancer specific and overall mortality: associations by metformin use and modification by race, body mass, and estrogen receptor status. PLoS ONE. 2020;15(5):e0232581. doi:10.1371/journal.pone.0232581
Boyle P, Boniol M, Koechlin A, et al. Diabetes and breast cancer risk: a meta-analysis. Br J Cancer. 2012;107(9):1608-1617. doi:10.1038/bjc.2012.414
Lega IC, Austin PC, Fischer HD, et al. The impact of diabetes on breast cancer treatments and outcomes: a population-based study. Diabetes Care. 2018;41(4):755-761. doi:10.2337/dc17-2012
Gegechkori N, Pak P, Wisnivesky JP, Lin JJ. Racial disparities in breast cancer mortality among women with diabetes mellitus. JCO. 2017;35(5_suppl):116-116. doi:10.1200/JCO.2017.35.5_suppl.116
Shahid RK, Ahmed S, Le D, Yadav S. Diabetes and cancer: risk, challenges, management and outcomesCancers (Basel). 2021;13(22):5735. doi:10.3390/cancers13225735
Centers for Disease Control and Prevention. Prevent type 2 diabetes.
Centers for Disease Control and Prevention. What can I do to reduce my risk of breast cancer?
The University of Texas MD Anderson Cancer Center. Diabetes and cancer: what you should know.
By Emily Brown, MPH
Emily is a health communication consultant, writer, and editor at EVR Creative, specializing in public health research and health promotion. With a scientific background and a passion for creative writing, her work illustrates the value of evidence-based information and creativity in advancing public health.

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