Breast Cancer Risk and Type 2 Diabetes

Recently, researchers out of Canada looked at the overall risk of breast cancer in both premenopausal women and postmenopausal women who have type 2 diabetes.

Results of their study appeared in the December 2011 issue of Diabetes Care in the article “Risk of breast cancer after onset of type 2 diabetes: evidence of detection bias in postmenopausal women.”

This study was a population-based retrospective cohort study.

The researchers used Cox regression stratified by premenopausal status (women who were younger than 55 years old) and postmenopausal status (women who were 55 years old or older) to estimate the hazard ratios for breast cancer. This was performed during earlier time windows (0 to 3 months) and later time windows (3 months to 10 years) after the diabetes index date.

What Did Researchers Learn about Breast Cancer Risk and Type 2 Diabetes?
The research team found that compared with women who did not have type 2 diabetes, the hazard ratio for breast cancer in the earlier time window was 0.95 (95% confidence interval [CI]: 0.48 to 1.86; p=0.88) in premenopausal women who had type 2 diabetes. And they found that the hazard ratio for breast cancer in the earlier time window was 1.31 (CI: 0.92 to 1.86; p=0.14) in postmenopausal women who had type 2 diabetes.

In addition, the research team found that the hazard ratio for breast cancer in the later time window was 0.92 (CI: 0.75 to 1.13; p=0.45) in premenopausal women who had type 2 diabetes. And they found that the hazard ratio for breast cancer in the later time window was 1.00 (CI: 0.90 to 1.11; p=0.93) in postmenopausal women who had type 2 diabetes.

At the end of the study, the researchers concluded that they observed an overall trend toward an increased risk of breast cancer in postmenopausal women who have type 2 diabetes. However, they noted that this trend was observed only in the time period that was immediately after the diabetes index date.