Excess weight can increase breast cancer risk, researchers say

Mother and daughter Angela and Candi Watts were both diagnosed with breast cancer in 2011. After a two-year battle, they are both disease-free, but the war continues.

The new enemy is their waistlines.

Scientists have discovered that excess weight not only raises the risks of getting cancer but the chances that cancer will return. Now, as medical studies seek to determine how much weight loss is needed for a better prognosis — and whether the fat-cancer link can be disrupted in other ways — patients are being encouraged to slim down.

"We need to do this for our health, now more than ever," said Angela Watts, 59, who is among the first survivors to benefit from a calorie-counting computer program provided by Johns Hopkins Hospital, where she was treated for stage 2 breast cancer. She dropped 5 pounds her first week.

The connection between fat and breast cancer, strongest in those diagnosed with the disease after menopause, is especially troubling given that two-thirds of the local and national population is overweight. Breast cancer remains the most common type of cancer for women, with more than 200,000 diagnoses and almost 40,700 deaths reported in 2009, the most recent year for which government statistics are available.

Doctors and public health officials have long been promoting lifestyle changes to stave off heart disease and diabetes, but they believe fewer people associate better diets and exercise with cancer prevention.

Cancer patients, meanwhile, face their own hurdles. They might have trouble dieting and exercising because treatment often makes them gain weight while experiencing fatigue and other side effects.

Given those challenges, researchers in Baltimore and across the country are seeking the best ways to change behaviors among those with a diagnosis and those who could be headed down that path.

Dr. Lewis E. Foxhall, who works on cancer-prevention policy at the University of Texas MD Anderson Cancer Center in Houston, said doctors don't know exactly how much weight loss improves a prognosis.

One often-cited study, published in 2009, tracked only those who had weight-loss surgery, which typically cuts much more body fat than diet and exercise, and keeps the fat off longer. Researchers also believe biological changes resulting from the surgery itself might have helped reduce women's risk of cancer.

Still, Foxhall, an American Cancer Society board member, recommends that doctors advise all their patients to diet and exercise and that public health officials get the message out.

"We need to pursue the things we know are associated with preventing cancer and help us deal with cancer once we get it," he said. "We need to address nutrition in the community and physical activity in schools and make sure people can make healthy choices."

Scientists theorize that obese women have elevated levels of hormones — including insulin, which regulates blood sugar; estrogen, a female sex hormone; and leptin, which helps regulate appetite — that lead to complex biological changes, including inflammation in the body that can promote cancer growth.

Some researchers are looking for ways to disrupt this link.

Dipali Sharma, an associate professor of oncology at Hopkins, wants to eventually develop a pill. After exploring the biology of many compounds, she's focusing on broccoli, garlic and the magnolia plant, whose properties show promise.

The therapy is a long way off — if it's possible — but important because "it's hard to tell someone just to lose a lot of weight," she said.

"If we know the pathways and the key players, we can develop a pill or capsule that can shut the pathways and tackle the key players and inhibit the link," Sharma said.

Dr. Vered Stearns, co-director of Hopkins' breast cancer program, will join with other U.S. and Canadian researchers during the next year in studying weight reduction among breast cancer survivors — including Angela Watts — and how much their long-term health improves. She will enroll up to 200 overweight women who completed treatment for breast cancer no more than five years ago.

Stearns provided Watts with the computer program and is "hopeful that our busy women will be able to adhere to the intervention that is both personalized and minimizes in-person visits."

Stearns added that all overweight women need to consider how their behavior affects their bodies.