Prospective association between red and processed meat intakes and breast cancer risk: modulation by an antioxidant supplementation in the SU.VI.MAX randomized controlled trial

Background: The level of evidence regarding the association between red and processed meat intakes and breast cancer risk is still low, due to insufficient prospective studies. Moreover, mechanistic data suggest that some antioxidants may modulate this relationship but epidemiological evidence is lacking. Our objectives were to investigate relationships between red and processed meat intakes and breast cancer risk, and to study whether an antioxidant supplementation modulates these associations, which, to our knowledge, has never been investigated before. Methods: The SU.VI.MAX study was a randomized, double-blind, placebo-controlled trial in which participants received a combination of low-dose antioxidants or a placebo from 1994 to 2002. This observational prospective analysis included 4684 women among whom 190 developed a first incident breast cancer between 1994 and 2007 [mean (range) follow-up = 11.3 (0-13) years]. Baseline dietary data were assessed by repeated dietary records in 1994-1995. Associations between quartiles of red and processed meat intakes and breast cancer risk were characterized by multivariate Cox proportional hazards models. Results: Breast cancer risk was directly associated with processed meat intake [ hazard ratio (HR)(Q4vsQ1) = 1.45 (0.92-2.27), P-trend = 0.03] and this association was stronger when excluding cooked ham [HRQ4vsQ1 = 1.90 (1.18-3.05), P-trend = 0.005]. In stratified analyses, processed meat intake was directly associated with breast cancer risk in the placebo group only [HRQ4vsQ1 = 2.46 (1.28-4.72), P-trend = 0.001], but not in the supplemented group [HRQ4vsQ1 = 0.86 (0.45-1.63), P-trend = 0.7]. Conclusion: Processed meat intake was prospectively associated with increased breast cancer risk. This study also suggests that antioxidants may modulate this association by counteracting the potential pro-carcinogenic effects of processed meat on breast cancer.