Cytochrome P450dbl phenotypes in malignant and benign breast disease

129 female patients with breast cancer and 79 controls undergoing biopsy for benign breast conditions had debrisoquine hydroxylator phenotype established. 129 female hospital patients with known hydroxylator phenotype were used as another control group. The breast cancer cases differed significantly from the benign controls in their debrisoquine phenotype, with 10% being poor metabolisers compared with none of the controls (P < 0.01). However, while a comparison of the distributions of metabolic ratio (an inverse measure of debrisoquine metabolism) of breast cancer patients and hospital controls showed a significant difference by rank, there was no significant difference in the proportion of poor metabolisers in these two groups. The cases with benign disease differed from the hospital controls in both metabolic ratio distribution (P < 0.001) and frequency of poor metabolisers (P < 0.05). Although there was a shift in metabolic ratio distribution, debrisoquine hydroxylator phenotype was not a genetic marker for breast cancer. Why no patients undergoing biopsies for benign conditions were poor metabolisers is unknown.