To estimate breast cancer risk conferred by individual SNPs, as well SNP-SNP interactions, we have studied 19 SNPs from 18 key cancer genes, involved in DNA repair (XPD, PTEN, GADD45), cell cycle (CCND1, p27, BARD1), carcinogen/estrogen metabolism (ESR1, CYP17, COMT, GSTP1, GSTM3, MTHFR), immune system (IL1a, IL10, IL13, TNFa, G-CSF) and others (MMP1) (Table 1). This evidence concerns the gene COMT and cancer.