GSTM1 null genotype, red meat consumption and breast cancer risk (The Netherlands)

Objective: We studied whether polymorphisms in N-acetyltransferase 1 and 2 and Glutathione S-transferase M1 and T1 genes modify the association between meat consumption and breast cancer. Methods: A nested case control was conducted in a Dutch prospective cohort. Breast cancer cases ( 229) and controls ( 264) were frequency matched on age, town and menopausal status. Results: There is no relation between any type of meat consumption (i.e., total meat, processed meat, fresh meat, red meat and white meat) and breast cancer risk. Neither presence of NAT1 or NAT2 rapid genotype, or GSTT1 null genotype, alone or in combination with meat consumption affects breast cancer risk. Absence of GSTM1 shows 46% increased breast cancer risk (OR = 1.46 (95% confidence interval, 95% CI = 1.02 - 2.09)). When stratifying according to combined 'GSTM1 genotype-meat consumption' categories, breast cancer risk is slightly increased with consumption of red meat both in women with genotype GSTM1 presence ( OR = 1.49 and 1.75 for intermediate and high versus low consumption) and in GSTM1 null genotype (OR = 1.18 and 1.02). These increases are statistically not significant. In postmenopausal women a suggestion of an effect of red meat consumption is observed: effects are slightly stronger, although still not statistically significant and without a clear dose - response relation: OR = 1.79 (95% CI = 0.92 - 3.50) and 1.46 (1.46 (95% CI = 0.76 - 2.82) for intermediate and high compared to low red meat consumption respectively. Reliable evaluation of interaction is not possible due to the small number of cancers. Conclusion: GSTM1 null genotype increases breast cancer risk. Red meat consumption slightly increases breast cancer risk, but the relation is not statistically significant and GSTM1, NAT1, NAT2 and GSTT1 polymorphisms do not modify this relation.