Abstract
Background: Dietary intake of antioxidant micronutrients, vitamins A, C and E, is reported to be associated with reduced carcinogenesis, and several case-control studies suggest these vitamins are associated with a reduced risk for breast cancer. Findings from cohort studies, however, are less consistent. To date, there are few studies that have examined the associations of vitamins A, C and E with breast cancer survival. Moreover, few studies have investigated differences in these associations by Hispanic (H) versus non-Hispanic white (NHW) ethnicity. This is important because previous research has indicated that these ethnic groups differ for both dietary antioxidant vitamin intake and survival. We evaluated the association of antioxidant vitamin intake with breast cancer survival and modification by ethnicity using data from a population-based study in New Mexico.
Materials and Methods: Survival data for this study were collected in the Long Term Quality of Life (LTQOL) study, which is a 12 to 15 year follow-up of women who participated in the New Mexico Women's Health Study (NMWHS), a population-based, case-control study of breast cancer conducted between 1992 and 1996. A total of 722 H and NHW cases, aged 20 to 80 years, were ascertained by the New Mexico Tumor Registry (year of diagnosis: 1992–1994). All nutritional information was collected at entry using a standardized food-frequency questionnaire. Death and cause of death was ascertained for cases from the National Death Index though 2008. Dietary intake and mortality data were available for a total of 686 (323 H and 363 NHW) women for these analysis. Generalized linear modeling (PROC GLM) was used to test for differences in antioxidant intake between H and NHW women, adjusting for total energy intake. Cox Proportional Hazards analysis was used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for the associations of vitamins A, C and E intakes with breast cancer survival, stratifying by ethnicity and adjusting for relevant covariates.
Results: After adjusting for total energy intake, H women had significantly (p<.0001) higher mean intakes of vitamin A, retinol, carotene, vitamin C, and E compared with NHW women. There were a total of 67 breast cancer deaths among Hispanics and 63 among non-Hispanic white women. The highest level of intake, compared to the lowest, for these antioxidant vitamins was not associated with survival in either ethnic group, adjusting for age, alcohol intake, smoking, BMI, energy intake, total fat intake, and physical activity. In H women, the hazard ratios were 0.99 (95%CI 0.49–1.99) for total vitamin A, 0.87 (95%CI 0.42–1.79) for retinol, 1.07 (95%CI 0.55–2.07) for carotene, 1.46 (95%CI 0.72–2.95) for total vitamin C and 0.69 (95%CI 0.27–1.75) for total vitamin E. Among NHW women results were: 1.05 (95%CI 0.50–2.19) for total vitamin A, 1.22 (95%CI 0.57–2.59) for retinol, 1.15 (95%CI 0.56–2.37) for carotene, 1.04 (95%CI 0.51–2.09) for total vitamin C and 1.26 (95%CI 0.55–2.89) for total vitamin E. Discussion: Although antioxidant vitamin intake was higher among Hispanic than non-Hispanic white women in the NMWHS study, higher consumption of these vitamins was not associated with survival in either ethnic group and cannot, therefore, explain differences between these ethnic groups for survival.
Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):B55.
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