Genotyping errors plague CYP2D6 testing for tamoxifen therapy — ScienceDaily
For years, controversy has surrounded the CYP2D6 gene test for breast cancer. Women with certain inherited genetic deficiencies in the CYP2D6 gene metabolize tamoxifen less efficiently, and thus have lower levels of tamoxifen’s active cancer-fighting metabolite endoxifen. Numerous studies have shown that these women gain less benefit from tamoxifen therapy and have higher rates of recurrence. However, two large clinical trials found no link between the CYP2D6 genotype and tamoxifen effectiveness, prompting recommendations against testing…