CHICAGO - SCIENTISTS know that being overweight increases the risk of breast cancers fed by estrogen, but being too fat may also increase the risk of triple-negative breast cancers, a less common and far more deadly type, US researchers said on Tuesday.
They said women who are overweight had a 35 per cent higher risk of developing triple-negative breast cancers, an aggressive form of cancer that affects 10 to 20 per cent of cases.
'The fact that we found an association with triple-negative breast cancer is unique because, biologically, this subtype is very different from other breast cancers,' said Amanda Phipps of the Fred Hutchinson Cancer Research Center in Philadelphia, whose study appears in the journal Cancer Epidemiology, Biomarkers & Prevention.
Breast cancer is the second-leading cause of cancer death among US women, after lung cancer. It kills 500,000 people globally every year and is diagnosed in close to 1.3 million people globally.
Most breast tumors are called estrogen-receptor positive because they are fueled by the hormone estrogen. About 20 per cent are HER2-positive, because a protein called HER2 is involved. A third type is driven by the hormone progesterone. These types of cancer can easily be treated.
Then there are triple-negative tumors, so named because they lack estrogen, progesterone or HER2 receptors needed for most breast cancer drugs to work.