Post-menopausal women with type II diabetes are at higher risk of developing breast cancer, researchers from the International Prevention Research Institute (i-PRI) and Cancer Research UK have found.
A study conducted on 56,000 breast cancer patients across four continents has found that post-menopausal women with type II diabetes have a 27 per cent increased risk of breast cancer.
The study did not find the same link between women of pre-menopausal age or those with type I diabetes.
"Our study found a significantly increased risk of breast cancer in women who had diabetes, which was restricted to those of post-menopausal age," said Professor Peter Boyle, President of i-PRI.
Researchers believe that high Body Mass Index (BMI), which is often associated with diabetes, may be an underlying contributing factor.
"We don't yet know the mechanisms behind why type II diabetes might increase the risk of breast cancer. On the one hand, it's thought that being overweight, often associated with type II diabetes, and the effect this has on hormone activity may be partly responsible for the processes that lead to cancer growth. But it's also impossible to rule out that some factors related to diabetes may be involved in the process," said Boyle.
Nearly 50,000 people are diagnosed with breast cancer each year in the UK. Among these, 4,000 cases of breast cancer are linked to excess bodyweight. The new study also claims that type II diabetes, which is caused due to obesity, increases the risk of postmenopausal breast cancer by up to 30 per cent.
"From this study, it's not clear whether there's a causal link between diabetes and the risk of breast cancer in post-menopausal women," said Martin Ledwick, researcher at Cancer Research UK.
"But as we know that having a high BMI can contribute to an increased risk of both type II diabetes and breast cancer, it makes sense for women to try and maintain a healthy weight."