Taking antidepressants with widely used cancer drug does not increase breast-cancer recurrence

PASADENA, Calif. A large study of patients with breast cancer who took the anti-cancer drug tamoxifen while taking an antidepressant were not found to have an increased risk of recurrence. The Kaiser Permanente study was published today in The Journal of the National Cancer Institute.

Tamoxifen is a commonly prescribed generic drug taken by women with breast cancer to reduce their chances of developing a recurrence. Tamoxifen is recommended for five years, but has notable side effects including hot flashes, night sweats and depression. Since hormone replacement therapy is not recommended to alleviate these symptoms in breast-cancer survivors, antidepressants have been increasingly prescribed for relief. Almost half of the 2.4 million breast-cancer survivors in the U.S. take antidepressants.

Previous studies have suggested that antidepressants reduce tamoxifen’s effectiveness in lowering subsequent breast-cancer risk.

Given that thousands of breast-cancer survivors struggle with depression, sleep disturbance, and other side effects while on tamoxifen, our study should help alleviate any concerns physicians have about prescribing antidepressants to their breast-cancer patients to help improve their quality of life, said Reina Haque, PhD, MPH, research scientist, Kaiser Permanente Southern California, Department of Research & Evaluation.

The study population consisted of 16,887 early-stage breast-cancer survivors treated with tamoxifen, as identified through electronic health records of Kaiser Permanente members in California. Nearly half – or 8,089 patients – were prescribed antidepressants.

The patients were followed for a maximum of 14 years and took tamoxifen an average of three years. (The median was 2.7 years.) Researchers found that 2,946 women (17.4 percent) subsequently developed breast cancer over the 14-year follow-up period. The majority of those women (2,512 or 14.9 percent) experienced breast-cancer recurrences in the same breast, while the remainder (434 or 2.5 percent) had cancer in the opposite breast.

We found no increased risk of recurrence, and this finding holds up regardless of the type of antidepressant used. This includes paroxetine, which had previously been reported to interfere with tamoxifen, Dr. Haque added. In addition, it is important to note that the rate of breast-cancer recurrence in our study is similar to the rate of recurrence found in other studies.

The study was supported by National Institutes of Health with additional support from the California Breast Cancer Research Program.

Other authors of the study include Jiaxiao Shi, PhD, Joanne E. Schottinger, MD, Syed A. Ahmed, MD, T. Craig Cheetham, PharmD, Joanie Chung, MS, Chantal Avila, MA, with Kaiser Permanente Southern California, Pasadena, Calif.; Ken Kleinman, PhD and Suzanne W. Fletcher, MD, MS, with Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, Mass.; and Laurel A. Habel, PhD, and Marilyn L. Kwan, PhD, with Kaiser Permanente Northern California, Oakland, Calif.

About the Kaiser Permanente Southern California Department of Research & Evaluation

The Department of Research & Evaluation conducts high-quality, innovative research into disease etiology, prevention, treatment, and care delivery. Investigators conduct epidemiology, health sciences and behavioral research, as well as clinical trials. Areas of interest include diabetes and obesity, cancer, HIV/AIDS, cardiovascular disease, aging and cognition, pregnancy outcomes, women’s and children’s health, quality and safety, and pharmacoepidemiology. Located in Pasadena, Calif. the department focuses on translating research to practice quickly to benefit the health and lives of Kaiser Permanente Southern California members and the general population. Visit kp.org/research.

About Kaiser Permanente

Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America’s leading health care providers and not-for-profit health plans. Founded in 1945, Kaiser Permanente has a mission to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 10 million members in eight states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: kp.org/share.