Avoidable breast cancer risk factors have been identified in a new study by scientists at the German Cancer Research Center.
The research team, led by Karen Steindorf and Jenny Chang-Claude, has been searching for risk factors that can be influenced by changes in lifestyle and behavior.
They focused on aspects such as taking hormones for relief of menopausal symptoms (hormone replacement therapy), physical activity, overweight and alcohol consumption. All these lifestyle factors have been identified in prior studies as possible risk factors for the development of breast cancer.
Of the modifiable lifestyle factors, it is primarily hormone replacement therapy and a lack of physical activity that increase a woman's risk of developing breast cancer.
Alcohol consumption and overweight were found to have less influence on breast cancer risk.
The study compared 6,386 healthy women with 3,074 breast cancer patients who had been diagnosed after the onset of menopause.
On the basis of this data, the researchers then calculated the percentage of cancer cases attributed to a particular risk factor or a particular combination of risk factors.
They determined that about 37 percent of all postmenopausal breast cancers are caused by non-modifiable factors, such as family history, age, or the age of first and last menstrual period.
They also determined that modifying certain lifestyle habits could prevent nearly 30 percent of breast cancers.
"That means that two factors which each woman has in her own hands are responsible for a similar number of postmenopausal breast cancer cases as the non-modifiable factors," said Steindorf.
The researchers have recommended women to take more exercise and to refrain from hormone replacement therapy unless it is absolutely necessary.