Diet and Exercise Inseparable for Breast Cancer Survival Benefit

SAN DIEGO, June 11 -- Breast cancer survivors who eat properly and exercise may halve their mortality risk regardless of obesity, researchers here found.
In a prospective observational study, women who ate five or more servings of vegetables and fruits a day and got the equivalent of 30 minutes of moderate exercise six days a week had a significant survival advantage (hazard ratio 0.56, 95% confidence interval 0.31 to 0.98), said John P. Pierce, Ph.D., of the University of California, San Diego, and colleagues.
This protective effect was seen for both obese and nonobese women, but not for women who focused on just one aspect of that healthy lifestyle, they reported in the June 10 issue of the Journal of Clinical Oncology.
Previous studies that looked at the impact of diet or physical activity on breast cancer survival had mixed results, but none of them evaluated both aspects together, the researchers said.
So, they analyzed the control group of the Women's Healthy Eating and Living Study, which is investigating a plant-based diet following breast cancer.
The 1,490 women included in the analysis had volunteered for the trial within four years of early-stage breast cancer diagnosis (mean two years). All had already completed primary therapy, although most were still on tamoxifen (Nolvadex).
Participants completed 24-hour dietary recall and physical activity questionnaires at baseline, then filled out health status questionnaires at five clinic visits over six years, with semiannual phone calls to report health events.
Average vegetable and fruit intake reported was 4.93 servings a day. Median physical activity was 636 metabolic equivalent task (MET)-minutes per week.
After an average of 6.7 years of follow-up, there were 236 breast cancer events and 135 total deaths, 118 from breast cancer and 10 from other cancers.
Since only seven deaths were not related to cancer, the mortality analyses reported by the researchers primarily referred to breast-cancer related mortality.
For the 30% of women who ate five or more servings of fruits and vegetables a day and accumulated at least 540 MET-minutes a week -- the equivalent of 30 minutes of brisk walking six days a week -- they found that mortality was significantly lower (hazard ratio 0.56, 95% CI 0.31 to 0.98).
Women who met these criteria for high fruit and vegetable and high physical activity had a 6% to 7% absolute 10-year mortality risk reduction compared with those who met only one criteria or neither of them (10-year survival 93% versus 86% to 87%).
Mortality increased as adherence to the criteria decreased (P=0.01 for difference). Mortality rates were:
4.8% with high diet and high exercise.
10.4% with low diet and high exercise.
10.7% with high diet and low exercise.
11.5% with low diet and low exercise.
High fruit and vegetable consumption without high physical activity did not significantly reduce mortality compared with poor diet and low physical activity (P=0.57).
Likewise, physical activity alone did not significantly reduce mortality (P=0.42).
Mortality was not associated with energy intake (P=0.10 for trend) or fiber consumption (P=0.12 for trend).
Less than one third (29%) of these breast cancer survivors were current drinkers, with 7% classified as heavy drinkers (60 drinks/mo). Alcohol consumption showed an inverse association with mortality (P<0.03)
Obese women had substantially higher mortality than nonobese women in every category except those who reported high fruit and vegetable intake and physical activity.
However, the researchers noted, fewer obese women met this pattern than their thinner counterparts (16% versus 30%).
"Among those who adhered to this healthy lifestyle, there was no apparent effect of obesity on survival," Dr. Pierce and colleagues wrote.
The effect was stronger in women who had hormone sensitive cancers, they said.
In the univariate analysis, women who had estrogen receptor-negative, progesterone receptor-negative tumors had no significant benefit from diet and exercise (P=0.4) whereas those positive for both hormone receptors did (P=0.01).
"Given that the number of cancer survivors is increasing, and breast cancer survivors make up the largest group of cancer survivors, it is important to consider the potential impact on prognosis of lifestyle changes such as diet and physical activity on women who have survived initial treatment," the researchers concluded.
Further study into the combined protective effect on breast cancer survival is warranted, they said.
The study was supported by the Walton Family Foundation and grants from the National Cancer Institute. The researchers disclosed no potential conflicts of interest.Primary source: Journal of Clinical OncologySource reference: Pierce JP, et al "Greater Survival After Breast Cancer in Physically Active Women With High Vegetable-Fruit Intake Regardless of Obesity" J Clin Oncol 25:2345-2351.