Abstract: The present invention provides methods for identifying a subject having an increased risk of developing an estrogen-related cancer, comprising determining which alleles of the genes encoding CYP1B1, CYP1A1, COMT, and GSTM1 are present in the genome of the subject so as to determine an estrogen metabolizing enzyme genotype for the subject, and correlating the estrogen metabolizing enzyme genotype of the subject to an increased risk of developing an estrogen-related cancer, for example, breast cancer. Also provided by the invention are diagnostic kits to determine the presence in a subject of the alleles of the genes encoding CYP1B1, CYP1A1, COMT, and GSTM1.

Abstract: The present invention provides methods for identifying a subject having an increased risk of developing cancer, for example, breast cancer, comprising determining the presence of the homozygous wild-type genotype of GSTM1, wherein the presence of the homozygous wild-type genotype of GSTM1 identifies a subject with increased risk of cancer. The present invention also provides methods for identifying a subject having a reduced risk of cancer, for example, breast cancer, comprising determining the presence of the homozygous null allele genotype of GSTM1, wherein the presence of the homozygous null allele genotype of GSTM1 identifies a subject with decreased risk of cancer. Also provided are isolated nucleotide sequences and kits for identifying the GSTM1 genotype in a subject.