Women With Diabetes Are More Often Diagnosed With Breast Cancer

Diabetes May Not, However, Be a Risk Factor for the Deadly Disease

A new study conducted by researchers at the University of Alberta in Canada, however, suggests that the reason women who have diabetes are more likely to be diagnosed with breast cancer is that doctors give them more tests.
 
Dr. Jeffrey A. Johnson and his colleagues at the School of Public Health at the University of Alberta in Calgary tracked 170,000 women in British Columbia for four to five years. Some of the women had been recently diagnosed (in the last 3 months) with type 2 diabetes and others had been diagnosed at least 3 months and up to 10 years earlier. Half of the women were 55 years of age or older, and half were younger than 55.

At the end of five years, the University of Alberta researchers observed that:

• Women who had been recently diagnosed with diabetes and who had not gone through menopause tended to be less likely to be diagnosed with breast cancer than women who had not gone through menopause and who did not have diabetes.
• Women who were diagnosed with diabetes in the past (3 months to 10 years before the study date) and who had not gone through menopause tended to be less likely to be diagnosed with breast cancer than women who had not been diagnosed with diabetes and who had not gone through menopause.
• Women who were diagnosed with diabetes in the past and who had gone through menopause were equally likely to be diagnosed with breast cancer as women who had never been diagnosed with diabetes and who had gone through menopause.

This gets a little hard to follow. The researchers did not find enough cases of breast cancer for statistically significant results, so they could only speak of tendencies, not absolutes. But if a woman has been diagnosed with diabetes a long time ago, she is actually less likely to be diagnosed with breast cancer before menopause. She is only equally likely to to be diagnosed with breast cancer after menopause. There was one group of women who were about 30% more likely to be diagnosed with breast cancer, newly diagnosed diabetics who were 55 or over, and assumed to have already passed menopause.

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Why should this be?

A new diagnosis of diabetes requires multiple doctor visits. Doctors make sure their female patients get mammograms after menopause. Presumably, more women get mammograms about the same time they start getting diabetes treatment, so more breast cancers are detected.

This does not mean that diabetes causes breast cancer. There is no evidence in this study that it does. In fact, since premenopausal diabetic women are less likely to be diagnosed with breast cancer, this study does not even suggest that the two diseases share common factors. The researchers attributed their findings to a "detection bias" causing more cancers to be detected because more tests were given.

If you are recently diagnosed with diabetes, don't worry that cancer is next. But do get regular checkups to catch both problems while they are relatively easy to treat.