The most widely investigated XPD polymorphisms in associations with cancer susceptibility comprise a nonsynonymous A>C substitution in exon 23 causing a lysine (Lys) to glutamine (Gln) substitution in codon 751 (Lys751Gln, rs1052559), a nonsynonymous G>A substitution in exon 10 leading to an aspartic acid (Asp) to asparagine (Asn) substitution in codon 312 (Asp312Asn, rs1799793), and a synonymous C>A substitution in exon 6 while conserving the arginine (R) residue in codon 156 (Arg156Arg, rs238406) [15]. Here, ERCC2 is linked to cancer.