A new analysis of 26 previous studies has reported that women who are heavy smokers and who carry common variants of a particular gene have a 40% higher risk of breast cancer. The meta-analysis was designed to investigate the relationship between the slow or rapid acetylation resulting from N-acetyltransferase 2 (NAT2) polymorphisms and risk of breast cancer. The studies included 9,215 cases and 10,443 controls.

No significant increases in breast cancer risk were found to be associated with NAT2 slow genotypes in the pooled data overall. Nor were significantly different risks found for Asians compared to Caucasians. When assessed by menopausal status, no statistically significantly increased risk was found for premenopausal or postmenopausal women. However, when stratified by cumulative smoking exposure, in smokers with high pack-years, NAT2 slow genotypes were found to be significantly associated with increased risk of breast cancer. The authors conclude that there is overall lack of association between NAT2 genotypes and breast cancer risk. However, NAT2 polymorphisms combined with heavy smoking history may contribute to breast cancer.