Study Suggests Link Between Diabetes, More Advanced-Stage Breast Cancer

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Several previous studies have found that women diagnosed with diabetes were more likely to be diagnosed with breast cancer than women who aren’t diabetic.

Now a Canadian study suggests that if diabetic women are diagnosed with breast cancer, it is more likely to be advanced-stage disease.

The study was published in the March 2015 issue of Breast Cancer Research and Treatment. Read the abstract of “The association between diabetes and breast cancer stage at diagnosis: a population-based study.”

The researchers looked at the medical records of 38,407 women from Ontario, Canada, who were diagnosed with breast cancer between 2007 and 2012; 6,115 (15.9%) of the women were diabetic. The women were 20 to 105 years old.

The researchers found that women with diabetes were:

  • 14% more likely to have stage II breast cancer
  • 21% more likely to have stage III breast cancer
  • 16% more likely to have stage IV breast cancer

rather than stage I breast cancer at diagnosis.

These differences in stage at diagnosis were statistically significant, which means they’re likely because the women had diabetes rather than just due to chance.

Compared to women who didn’t have diabetes, women with diabetes also:

  • had a higher risk of the cancer spreading to the lymph nodes
  • were less likely to have a mammogram

The researchers suggested that breast cancer screening may need to be more aggressive for women with diabetes so that if any cancer develops it is found at an earlier stage. A more aggressive screening plan may include screenings every 6 to 12 months -- possibly an annual mammogram and an annual breast MRI or ultrasound.

It’s not clear why women with diabetes may have a higher risk of being diagnosed with more advanced-stage breast cancer. Higher insulin levels may be part of the reason. Insulin is a hormone that helps our bodies regulate blood sugar. Insulin also helps cells grow. People with diabetes tend to have insulin levels that are higher than normal. This is partially because their bodies no longer respond to normal levels of insulin. Some experts think that higher insulin levels in people with diabetes may help breast cancer cells develop and grow, which could increase the risk of a later-stage diagnosis.

While genetics play a role in developing diabetes, many people are diagnosed with the condition because of an unhealthy diet and lifestyle: too much sugar and too many simple carbohydrates, combined with not enough exercise. One of the best ways to avoid diabetes and help keep your breast cancer risk as low as it can be is to have a healthy diet and lifestyle:

  • eat a diet low in added sugar and processed foods and rich in fruits and vegetables
  • maintain a healthy weight
  • exercise regularly -- every day if you can -- at a moderate intensity
  • avoid alcohol
  • don’t smoke

Visit the Lower Your Risk section to learn more about breast cancer risk and steps you can take to make yours as low as it can be.

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