Vegetables Reduce the Risk of Breast Cancer Recurrence
Design
Secondary analysis from the Women’s Healthy Eating and Living Study (WHEL study)
Participants
3,080 female breast cancer survivors aged 18–70, who were on average 23.5 months post-diagnosis at the time of enrollment. All participants lived in 4 western states, and the WHEL trial was conducted between the years of 1995 and 2006. Participants were diagnosed with and had completed treatment for stage I, II, or III invasive breast cancer, and at the time of enrollment were found to be without evidence of disease. The majority of participants were educated, nonsmoking, sedentary Caucasian women.
Study Parameters Assessed
The WHEL study intervention diet included a daily diet of 5 vegetables (a vegetable serving was defined as any ½-cup serving of raw or cooked vegetables or 1 cup of raw leafy vegetables excluding iceberg lettuce and white potatoes), 3 fruits, 16 oz. vegetable juice, 30 g fiber, and 20% energy from fat. The WHEL Study protocol included a baseline clinic visit to assess baseline characteristics. Dietary intakes were then assessed in 24-hour dietary recalls in 4 prescheduled telephone calls. At study entry (baseline), participants completed questionnaires regarding menopause history, use of menopausal hormone therapy, other lifestyle behaviors and cancer occurrence. Cancer outcomes were assessed from annual self-administered questionnaires, with 93% of cancers confirmed with a review of pathology reports.
In this secondary analysis, a separate subgroup analysis was performed on the effect of vegetable intake on recurrence in women taking tamoxifen compared to women not taking tamoxifen. Furthermore, the effect of cruciferous vegetable intake on recurrence rate in tamoxifen users was assessed.
Key Findings
WHEL participants reported mean baseline intakes of 3. 1 servings of total vegetables and 0.5 servings of cruciferous vegetables. Women in the highest tertile of vegetable intake had a significantly lower hazard of breast cancer recurrence (HR 0.69, 95% CI: 0.55–0.87) at baseline. Cruciferous vegetable intake did not produce a statistically significant decrease in the hazard of recurrence at baseline. This secondary analysis revealed that when stratified for tamoxifen use, hazard of recurrence was even lower in women in the highest tertile of vegetable intake versus non-tamoxifen users (HR 0.56, 95% CI: 0.41–0.77, P≤0.001). Furthermore, a statistically significant reduction in the hazard of recurrence was seen with cruciferous vegetable consumption in the tamoxifen users (HR 0.65, 95% CI: 0.47–0.89, P=0.006).
Practice Implications
This secondary analysis adds to the growing number of secondary analyses of the WHEL study that elucidate benefit from vegetable intake in subpopulations of the participants. Although the WHEL study ultimately failed to find benefit from consumption of vegetables in reducing the risk of breast cancer recurrence, subsequent secondary analyses of various cohorts, such as this one, are finding benefit.