Impact of diet or physical activity on breast cancer survival

Breast cancer survivors who eat a healthy diet and exercise moderately can reduce their risk of dying from breast cancer by half, regardless of their weight, suggests a new longitudinal study from the Moores Cancer Center at the University of California, San Diego (UCSD).

Previous studies have looked at the impact of diet or physical activity on breast cancer survival, with mixed results. This study, published in the June 10 issue of the Journal of Clinical Oncology, is the first to look at a combination of both in breast cancer.

"We demonstrate in this study of breast cancer survivors that even if a woman is overweight, if she eats at least five servings of vegetables and fruits a day and walks briskly for 30 minutes, six days a week, her risk of death from her disease goes down by 50 percent," said the paper's first author, John Pierce, Ph.D., director of the Cancer Prevention and Control Program at the Moores UCSD Cancer Center. "The key is that you must do both."

The study looked at 1,490 women aged 70 years and younger (average 50 years) with early stage breast cancer who were randomly assigned to the non-intensive dietary arm of the ongoing Women's Health Eating and Living (WHEL) study. The WHEL study is a multi-center study, based at UCSD, investigating the effect of a plant-based diet on additional breast cancer events.

The women in the study were diagnosed with early stage breast cancer between 1991 and 2000 and had completed their primary therapy prior to enrollment. Dietary pattern and physical activity were assessed at enrollment and the women were followed for between five and 11 years.

The researchers found that only 16 percent of women who were obese were both physically active and had a healthy diet, compared to 30 percent in the rest of the study population. Those who were both physically active and had a healthy diet were much more likely to survive through the follow-up period than the rest of the study group. The mortality rate was 7 percent, approximately half of that seen for the rest of the study population.

"Of particular importance is that this halving of risk was seen in women who were not obese as well as in those who were obese," said co-author Cheryl Rock, Ph.D., R.D., of the Center's Cancer Prevention and Control Program. "Also, the effect was not seen in women who practiced only one of the lifestyle patterns , high vegetable and fruit intake, or physical activity."

Because of the strength of the findings from this longitudinal (observational) study, the researchers want to further investigate the combined protective effect of diet and physical activity on breast cancer survival in an interventional study in which they will change the diet and level of physical activity in breast cancer survivors.

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