Exercise, keeping weight down help prevent breast cancer recurrence, review finds

Women who've survived breast cancer can reduce their risk of recurrence by avoiding weight gain and getting consistent exercise, a new Canadian review suggests. 

The researchers reviewed 67 published research articles or reviews focused on lifestyle factors, such as exercise, weight, diet and smoking, to weigh how patients with breast cancer can improve their prognosis.

Physical activity can reduce breast cancer mortality by about 40 per cent, previous research suggests.

It has the "the most powerful effect of any lifestyle factor on breast cancer outcomes," Dr. Ellen Warner of Sunnybrook Health Sciences Centre in Toronto, and her co-author Julia Hamer write in Monday's issue of the Canadian Medical Association Journal.

Warner tells patients exercise is part of their treatment.

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"Following the recommended 150 minutes of moderate to vigorous exercise or 75 minutes of vigorous exercise per week, along with two to three weekly sessions of strength training, can help reduce the risk of breast cancer recurrence and mortality."

Weight gain during or after breast cancer treatment is linked to deaths related to the disease, Warner and Hamer said.

For instance, weight gain of more than 10 per cent of body weight after a breast cancer diagnosis increases breast cancer mortality. But there are good reasons to discourage more moderate weight gain, the experts said, given its harmful effects on mood and body image.

They said it's common for patients to reduce their level of physical activity after a breast cancer diagnosis, but health professionals such as onocologists can promote and encourage their patients to work out.

Quit smoking, too

In previous studies, researchers have speculated that physical activity may lower breast cancer mortality by lowering hormone levels or by acting on non-hormone pathways, such as weight control.

Quitting smoking is also encouraged. Even though it's unclear if butting out affects recurrence of breast cancer, the risk of death from smoking-related health issues is a strong reason to quit, the reviewers said.

Other key points included:

• All patients with breast cancer (except those with an abnormally low body mass index before diagnosis) should avoid weight gain. It's unclear whether weight loss improves prognosis.
• Soy consumption is not harmful.
• No specific type of diet has been shown to reduce the risk of breast cancer recurrence.
• Limiting alcohol consumption to one or fewer alcoholic drinks per day may help reduce the risk of a second breast cancer.

The information on diet is valuable, said Leslie Bernstein, a professor in the department of population sciences at the City of Hope Comprehensive Cancer Center in Duarte, Calif. She reported on the link between exercise and reduced breast cancer risk decades ago.

Many women have avoided soy in their diets for fear of cancer recurrence.

The estrogens in soy are "so weak" that the evidence does not support avoiding them, Bernstein said. "Of course, everything in moderation," she told HealthDay News. 

The reviewers called a cancer diagnosis a "teachable moment" when patients are more receptive to healthy lifestyle changes that will improve their overall health.

Improving lifestyle can also offer a psychological boost, they said, by empowering patients. "The feeling of loss of control is one of the biggest challenges of a cancer diagnosis."

But they don't want patients to feel that inadequate lifestyle changes have led to  recurrence since some breast cancers are so aggressive in nature.