Regular physical activity could play a role in helping women at high-risk of breast cancer delay the need for drastic preventive measures, such as prophylactic mastectomy, according to US research.
The results of the WISER Sister study help clarify the emerging connection between exercise and breast cancer risk, according to researchers from the University of Pennsylvania.
“Exercise could delay the diagnosis, and reduce the stage and grade and severity of the tumour when it is diagnosed”
As a result of their findings, the study authors suggest that women who have an elevated breast cancer risk should consider doing 30 to 60 minutes of aerobic activity per day for five days per week.
For their study, they recruited 139 premenopausal women aged 18-50 who were all deemed high-risk for breast cancer due to mutations in the BRCA genes or family history.
One group performed a treadmill exercise 150 minutes per week and another exercised twice that amount. In addition, a control group exercised for less than 75 minutes per week.
Each woman provided blood and urine samples, and also underwent MRI breast imaging, before and after each of five menstrual cycles.
Over the course of the study, the control group showed a 20% increase in oestrogen-sensitive breast tissue, whereas the other two groups saw reductions of about 8% and 12% respectively – implying a drop of about 10% per 100 minutes of exercise.
The study results have just been published in the journal Breast Cancer Research and Treatment.
The study authors suggested that oestrogen was likely to be a significant factor in the relationship between aerobic exercise and reduced breast cancer risk, as it normally stimulated an increase in breast cells.
“Double mastectomy is considered an effective method of prevention, but that’s an incredibly difficult decision”
Previous studies have suggested that even moderate exercise can significantly lower oestrogen levels, and intense exercise, such as that practiced by female athletes, commonly leads to sharp drops in oestrogen levels, breast shrinkage, and irregular or even absent periods.
Study author Professor Kathryn Schmitz said: “It makes sense that if your body is too busy doing other things, such as exercising regularly, it’s going to know that it can’t sustain other oestrogen-dependent functions – including spreading cancerous cells – and thus will start to shut them down.”
She highlighted that women at an increased risk of breast cancer had “no easy option” for avoiding cancer and that the decision to have a double mastectomy was an “incredibly difficult” one to make.
“These new results show that for women in this high risk category, aerobic exercise has a striking ability to reduce the hormonally sensitive tissue in the breast that we worry about most for breast cancer,” she said.
She added: “We understand that exercise isn’t a panacea that will prevent cancer from occurring in women at high risk. However, we do believe that exercise could delay the diagnosis, and reduce the stage and grade and severity of the tumour when it is diagnosed.”
Professor Schmitz said she often met woman who had found out they were BRCA positive and asked her whether exercise would help them until they had made a decision about surgery.
“For years I had to say ‘I don’t know’. Now I can say the research suggests it’s possible,” she said.