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Bringing Ideas to Life: Breast Cancer Pharmacogenic Testing 05.07.07 (continued from previous page) Clinical testing in the area of pharmacogenomics has great potential to impact patient care. But although markers of both drug metabolism and toxicity have been identified, testing for these markers has not yet been widely adopted by clinicians. Recently an FDA advisory committee recommended that patients receiving the breast cancer drug tamoxifen be tested for variations in the gene (Cytochrome P450 2D6) primarily responsible for metabolizing tamoxifen into its active form, endoxifen. Although there is clear data indicating that patients who are poor metabolizers of tamoxifen are at increased risk of breast cancer recurrence, the impact of this information on patient care is still unclear. The only test cleared by the FDA for comprehensive analysis of variations in the CYP2D6 gene is the Roche Diagnostics AmpliChip CYP450 Test. Tim Hamill, MD, director of the UCSF Clinical Laboratories, had worked with industry before, mostly as a test site for new equipment and applications. But last October, when the FDA panel made its recommendation to test the CYP2D6 gene in patients on Tamoxifen, Dr. Hamill and Laura Esserman, MD, the director of the Carol Franc Buck Breast Care Center, wanted to offer this test to breast cancer patients to clarify its clinical use. "With any of these new tests, there is uncertainty in the beginning about the strength of the data suggesting a change in practice," notes Dr. Esserman. "We will continue to learn from this program, and others around the country, as they are developed." Importantly, there are therapeutic alternatives, such as aromatase inhibitors, available if the tests indicate that tamoxifen will not lead to a favorable outcome. Industry partner Roche Diagnostics developed the AmpliChip CYP450 Test using Affymetrix microarray technology, which enables the test to offer more comprehensive analysis of CYP2D6 variations. "We wanted to increase pharmacogenomic testing capability at UCSF using this test as a pilot study, and approached Affymetrix and Roche," Hamill says. "We knew there was value for both partners: We would gain access and know-how to their technology, and we would have the opportunity to study and provide them with information about the psychosocial and clinical decision-making process that occurs around taking that test."
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