Popular Antidepressant Linked to Increased Breast Cancer Mortality

Findings from research led by Catherine M. Kelly, a recent graduate of HPME’s MSc – Clinical Epidemiology and Health Care Research program, have major implications for the treatment of thousands of breast cancer patients.

Up to 25 per cent of patients with breast cancer experience a depressive disorder. In addition to being treated with tamoxifen to combat their cancer, many of these patients receive antidepressant therapy. Kelly (a researcher at the M.D. Anderson Cancer Center in Houston, Texas) and her team found a strong association between an increased risk of death from breast cancer among people treated with both tamoxifen and paroxetine, a commonly prescribed antidepressant (brand name: Paxil).

"Co-prescribing of tamoxifen and selective serotonin reuptake inhibitors (SSRIs) such as paroxetine to combat depression is quite common," Kelly says. "Unfortunately, we found that paroxetine can irreversibly reduce or abolish the survival advantage conferred by long-term tamoxifen therapy among breast cancer patients. The data clearly show that the choice of antidepressant can significantly affect survival in women receiving tamoxifen for breast cancer."

The study examined 2,430 women aged 66 years or older with breast cancer living in Ontario who were treated with tamoxifen between 1993 and 2005. Thirty per cent of these women also received antidepressants, and paroxetine was the most commonly used SSRI.

The results of Kelly and her team’s study appeared in the British Medical Journal. The journal expedited the paper’s publication because of the importance of its findings – in particular, their public health implications. The story was picked up by Canadian and international media, including The Globe and Mail, CTV News, CBS News, and Reuters.

Kelly’s research formed the basis of the thesis she completed while an HPME student. In recognition of the outstanding paper based on her thesis, Kelly received HPME’s Thomas and Edna Naylor Memorial Award in spring 2010.

For more information:

Kelly, C.M., Juurlink, D.N., Gomes, T., Duong-Hua, M., Pritchard, K.I., Austin, P.C., & Paszat, L.F. (2010). Selective serotonin reuptake inhibitors and breast cancer mortality in women receiving tamoxifen: A population based cohort study. BMJ, 340: c693.