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

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, and the risk of recurrence was similar in women who took antidepressants as among those who did not use antidepressants.

"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.