Greater survival after breast cancer in physically active women with high vegetable-fruit intake regardless of obesity

Abstract

Purpose: Single-variable analyses have associated physical activity, diet, and obesity with survival after breast cancer. This report investigates interactions among these variables.

Patients and methods: A prospective study was performed of 1,490 women diagnosed and treated for early-stage breast cancer between 1991 and 2000. Enrollment was an average of 2 years postdiagnosis. Only seven women were lost to follow-up through December 2005.

Results: In univariate analysis, reduced mortality was weakly associated with higher vegetable-fruit consumption, increased physical activity, and a body mass index that was neither low weight nor obese. In a multivariate Cox model, only the combination of consuming five or more daily servings of vegetables-fruits, and accumulating 540+ metabolic equivalent tasks-min/wk (equivalent to walking 30 minutes 6 d/wk), was associated with a significant survival advantage (hazard ratio, 0.56; 95% CI, 0.31 to 0.98). The approximate 50% reduction in risk associated with these healthy lifestyle behaviors was observed in both obese and nonobese women, although fewer obese women were physically active with a healthy dietary pattern (16% v 30%). Among those who adhered to this healthy lifestyle, there was no apparent effect of obesity on survival. The effect was stronger in women who had hormone receptor-positive cancers.

Conclusion: A minority of breast cancer survivors follow a healthy lifestyle that includes both recommended intakes of vegetables-fruits and moderate levels of physical activity. The strong protective effect observed suggests a need for additional investigation of the effect of the combined influence of diet and physical activity on breast cancer survival.

Fig 1

Kaplan-Meier survival after Women’s Healthy Eating and Living (WHEL) Study enrollment by four diet and physical activity categories. Low vegetables-fruits (VF), less than 5 servings/d; high VF, ≥ 5 servings/d; low physical activity (PA), less than 540 metabolic equivalent task (MET) -min/wk; high PA, ≥ 540 MET-min/wk. Survival is plotted as a function of number of years enrolled in WHEL Study.

Fig 2

Mortality by diet and physical activity (PA) in Women’s Healthy Eating and Living Study comparison group: body mass index (BMI) categories. Bars show proportion (SE) for all-cause mortality by baseline BMI category. Low vegetables-fruits (VF), less than 5 servings/d; high VF, ≥ 5 servings/d; low PA, less than 540 metabolic equivalent task (MET) -min/wk; high PA, ≥ 540 MET-min/wk. BMI was calculated as weight in kilograms/height in square meters.

Fig 3

Mortality by tumor hormone receptor status and lifestyle in Women’s Healthy Eating and Living Study comparison group. Bars show proportion (SE) for all-cause mortality by baseline tumor estrogen receptor (ER) and progesterone receptor (PR) status (+, positive; −, negative), dietary intake of vegetables-fruits (VF), and physical activity (PA). Low VF, less than 5 servings/d; high VF, ≥ 5 servings/d; low PA, less than 540 metabolic equivalent task (MET) -min/wk; high PA, ≥ 540 MET-min/wk.