Dietary Associations with Biomarkers of Breast Cancer Risk in Women on Adjuvant Tamoxifen Therapy

Abstract

Dietary components potentially influence breast cancer risk factors, including breast density (BD) and estrogen metabolism (EM). Tamoxifen (TAM) is a commonly prescribed anti-estrogen adjuvant cancer treatment to reduce breast cancer risk, partially through modulation of BD and EM. Epidemiological evidence has suggested a potential protective effect from dietary intakes of fiber and vegetables in breast cancer recurrence in women on TAM as well as an independent influence on BD and EM. The relationship between dietary intake BD and EM in women prescribed TAM is not fully understood. A cross-sectional analysis using baseline data collected from 130 pre- and post-menopausal women taking TAM and enrolled in the Diindolylmethane Efficacy (DIME) Study was conducted. Participants completed the Arizona Food Frequency Questionnaire to assess dietary intake. TAM metabolites were analyzed through HPLC. BD was measured from digital mammograms and urinary EM was analyzed using LC/MS. Unadjusted linear regression between diet and four TAM metabolites indicated significant association between endoxifen and caffeine. 4-hydroxyTAM had significant inverse associations with fat intake, including monounsaturated, polyunsaturated and saturated fats. Linear regression adjusted for BMI revealed a statistically significant positive association with caffeine intake and BD, with no other dietary associations observed. The highest amount of correlations was observed between 2OHE and energy, total fat, MUFA, PUFA, protein and carbohydrate intake, though weak. Correlations were seen between 4OHE, 16αOHE and total isoflavones. Cholesterol was weakly positively correlated with 2mOHE, E1 and approached significance with E2. Dietary intake shows little association with BD or EM in women taking TAM therapy. Alternate preventive mechanisms for diet in women on TAM therapy should be investigated.