David A Flockhart, MD, PhD, Division Chief of the IU Department of Medicine’s Division of Clinical Pharmacology and PredictER Collaborator, was featured in a December 29th New York Times article that is part of a compelling series examining steps taken toward medicine based on evidence. The article, Patient’s DNA May Be Signal to Tailor Medicine, provides a highly readable overview of personalized medicine, illustrates the field’s inherent potential to increase positive outcomes and decrease costs, and then discusses some of the conundrums that genetically-tailored medicine presents. The author, Andrew Pollack, uses the outcomes of Flockhart’s extensive tamoxifen research to aptly illustrate the medical promise of genetic testing and its broader implications. Flockhart’s research demonstrates that a particular enzyme, CYP2D6, is responsible for converting tamoxifen into a different substance, called endoxifen, which is then directly responsible for fighting breast cancer. The CYP2D6 gene, however, varies between people such that the mechanism is inactive in about 7% of the population, and only moderately active in 20-40%. As the article points out, most patients are now treated with a more expensive class of drugs that demonstrated greater efficacy in clinical trials conducted before the role of CYP2D6 was fully understood. For those women with active CYP2D6, however, tamoxifen may well be the better alternative for the patient, both medically and economically. Genetic testing to determine gene activity in this scenario may therefore have vast economic implications for the pharmaceutical industry.
Amy Lewis Gilbert