Ray reactions of normal tissues in breast cancer patients, relation with allelic COMT gene

The study was designed to compare the severity of normal tissue reactions to radiation therapy in cancer patients with different genotypes at the polymorphic site COMT*H/L. The COMT gene encodes for a protein involved in deactivation of genotoxic estrogen species, and the protein product encoded by the L (low activity) allele is 3-5-fold less active than its counterpart encoded by the H (high activity) allele. The study group included 91 breast cancer patients, who received radiation therapy; total local doses were 50-60 Gy. Tissue reactions were classified as three groups, namely expressed, moderate, and no reaction. Genotypes at the polymorphic site were determined by PCR-RFLP technique. It was found that individual radiation reaction was associated with the L allele frequency: 0.46 in patients without radiation reactions, 0.52 in patients with moderate reactions, and 0.64 in patients with expressed radiation reactions of normal tissues. The observed tendency was statistically significant (p