Weight increases breast cancer risk

Women who have risk factors commonly associated with Type 2 diabetes also have much greater odds of being diagnosed with an advanced breast cancer, according to research.

University of Melbourne researcher Dr Anne Cust was a key collaborator on an international study which was presented to the Population Health 2008 Conference in Brisbane.

The study found that women who were overweight or had signs of insulin resistance – such as elevated blood glucose or insulin levels – were about 50 per cent more likely to be diagnosed with an advanced breast cancer tumour.

Researchers tracked more than 60,000 Swedish women over a 20-year-period from 1985 to 2005. All were cancer free when recruited and their blood tested for glucose, insulin and other hormones associated with obesity and diabetes risk.

Insulin resistance is most commonly caused by being overweight and inactive and is often a precursor to Type 2 diabetes.

Dr Cust said that previous research had shown a strong link between being overweight and increased breast cancer risk in post menopausal women– but this study was the first to demonstrate the influence of insulin resistance on the stage of cancer diagnosis.

“Women with insulin resistance or who were overweight were less likely to be diagnosed with stage 1 breast cancers but at greater risk of being diagnosed with stage 2 to 4 tumours – larger more advanced cancers,’’ she said. “We know that being overweight and having insulin resistance is a risk factor for getting cancer but – in the case of breast cancer – our study indicates that the cancer will be more advanced.”

Dr Cust said the research findings were particularly significant at a time when there were major public health concerns about obesity and Type 2 diabetes rates.

Dr Cust’s research was conducted with colleagues from Umea University, Sweden, and the German Cancer Research Centre. It has been published in the journal Breast Cancer Research and Treatment. 

(Source: Breast Cancer Research and Treatment: University of Melbourne: July 2008)