Tamoxifen, Antidepressants, and CYP2D6: The Conundrum Continues

Extract

For a decade, a case has been building that a certain group of antidepressants, known as selective serotonin reuptake inhibitors (SSRIs), interfere with the breast cancer drug tamoxifen by inhibiting the enzyme CYP2D6. Two studies featured at the American Society of Clinical Oncology (ASCO) annual meeting came down on opposite sides of that question, causing a flurry of press reports and reigniting debate over the role of antidepressants and CYP2D6 in patients’ response to tamoxifen.

The conflicting results did little to answer the question of whether SSRIs affect the clinical efficacy of tamoxifen, but they brought the issue into the spotlight, drawing attention to the lack of data to guide clinical practice. The findings also highlighted the importance of related research on the effect of CYP2D6 variants on tamoxifen response—another major issue in breast cancer treatment.

Do SSRIs affect breast cancer recurrence in patients taking tamoxifen? Based on research to date, “the short answer is yes and no,” said Lori Pierce, M.D. , who discussed the two conflicting abstracts as highlights of the ASCO session on adjuvant therapy for breast cancer. “We need additional validation studies,” she said, “before we can make recommendations regarding CYP2D6 function and routine testing in patients who are taking tamoxifen.”