By Jimmy Downs

Sunday Spet 23, 2012(foodconsumer.org) -- A new review study in British Journal of Cancer suggests that women with type 2 diabetes mellitus are at higher risk for breast cancer.

P. Boyle of International Prevention Research Institute in Lyon, France and colleagues meta-analysed data from observational epidemiological studies and found that overall women with type 2 diabetes mellitus were 27 percent more likey to have breast cancer, compared with those without the disease.

Different studies yielded slightly different results.  Prospective studies showed women with type 2 diabetes were 23 percent more likely to have breast cancer, compared to 36 percent increase in the risk estimated in retrospective studies.

Studies that adjusted for body mass index showed women with type 2 diabetes were 16 percent increased risk for breast cancer whereas studies that did not adjust for BMI showed the risk was increased by 33 percent in women with diabetes.

Type 1 diabetes or type 2 diabetes in pre-menopausal women was not found associated with risk of breast cancer.

The researchers concluded "The risk of breast cancer in women with type 2 diabetes is increased by 27%, a figure that decreased to 16% after adjustment for BMI. No increased risk was seen for women at pre-menopausal ages or with type 1 diabetes."

M. T. Redaniel of University of Bristol in Bristol, UK and colleagues reported in Cancer Causes and Control  a case-control study that showed women with breast cancer who also suffered type 2 diabetes mellitus were 40 percent more likely to die from all causes, compared with those with breast cancer only.

Wei-Wu Chen of  National Taiwan University Hospital, Yun-Lin Branch in Yunlin, Taiwan and colleagues also reported in the Oncologist that breast cancer patients who had type 2 diabetes mellitus had a higher risk of dying from all causes and of breast cancer, compared to those who did not have diabetes mellitus.

One explanation for the association between breast cancer and type 2 diabetes is that diabetes patients tend to be insulin insensitive or resistant and have to produce more insulin than healthy people in order to deal with blood sugar.  When insulin is produced, insulin-like growth factor-1, which is known to promote cancer growth,  is also produced.  Therefore, type 2 diabetes patients tend to produce more insulin-like growth factor-1 than those without diabetes and they are at high risk for cancer.

Some diabetes treatments may also increase risk of developing breast cancer or death of patients with breast cancer.  Breast cancer patients who happen to also have type 2 diabetes need to do some homework to understand which diabetes treatment is best for them.  Not all treatments are the same.