Antidepressants may be linked to a risk of breast and ovarian cancer, according to researchers from the University of Massachusetts Boston and Harvard University.
The risk of cancer increased 11 percent on average for patients taking antidepressants, according to a report that analyzed previous data and was published in today’s issue of the peer-reviewed journal PLoS ONE.
The researchers analyzed 61 studies and found 20 that identified a link. The connection was stronger in cases of the most widely used of the drugs, selective serotonin reuptake inhibitors, or SSRIs. Of 16 studies that looked at this class of drugs, which include GlaxoSmithKline Plc’s Paxil, 15 detected a higher chance of cancer, according to the paper.
The findings point to a need for more research on SSRI use in women and the link to cancer, said Lisa Cosgrove, the report’s main author.
“I feel very strongly, as a researcher and as a women, about the issue of informed consent,” said Cosgrove, a research lab fellow at Harvard’s Edmond J. Safra Center for Ethics in Cambridge, Massachusetts, and an associate professor of psychology at the University of Massachusetts Boston. “I would want to consider nondrug treatment if I was mildly depressed, given our data.”
Antidepressants, used by 27 million Americans, are the third most-prescribed class of drug in the U.S. behind cholesterol- lowering medications and painkillers. SSRIs, which raise levels of the chemical serotonin in the brain, have been shown to increase suicidal thoughts and behavior in teenagers and children, and the U.S. Food and Drug Administration in 2004 ordered that the medications carry the strictest warning on their labels.
The first SSRI was Eli Lilly & Co. (LLY)’s Prozac, approved by the FDA in 1987. A message left for Mark Taylor, a Lilly spokesman, wasn’t immediately returned, and a call to his mobile phone wasn’t answered. Sarah Alspach, a spokeswoman for GlaxoSmithKline Plc (GSK), the London-based maker of Paxil, declined to comment because no one at the company had the opportunity to review the study.
Cosgrove and her five collaborators analyzed 26 epidemiological and 35 pre-clinical studies conducted between 1965 and 2010 that tested for a link between antidepressants and breast or ovarian cancer. The increase in the risk of cancer was based on a meta-analysis of the 26 epidemiological studies.
Of the 16 studies on SSRIs, only four found a statistically significant positive association with cancer, based on the original conclusions of the studies.
A meta-analysis is often done when the initial studies were unable to come to a strong conclusion, were small, or the results were mixed, according to Milayna Subar, national practice leader in oncology for Franklin Lakes, New Jersey-based Medco Health Solutions Inc., a pharmacy benefits company.
“I would not have thought it to be an open question, but a question can be opened again when new data come out,” said Subar, who said she hadn’t seen the PLoS ONE study. “If new data come out and they change the current thinking, it will be debated again.”
The researchers also found differences in the conclusions of studies in which the lead investigator had a connection to a maker of antidepressants and those headed by an independent scientist, according to report. In the 15 cases where there was a drugmaker link, not one study found a cancer link. Of the 46 others, 43 percent cited a risk, the researchers said.
The drug companies weren’t identified in the report. A researcher connection was defined as working for an antidepressant maker; receiving honoraria, research funding or support from one; holding equity in, consulting for or being on the board of such a company; or holding a patent, patent application or royalties on an antidepressant medication.
“The question is certainly open about the link between cancer and antidepressants, but we can say that researchers with industry ties are far less likely to publish studies that link a serious adverse effect to a popular drug class,” said Cosgrove, a critic of ties between psychiatrists and drugmakers.
Doctors wrote 168 million prescriptions for antidepressants in 2009, making them the third most-prescribed class of drugs, generating $9.9 billion in sales, according to IMS Health, a Norwalk, Connecticut-based market research firm.
SSRIs were the most widely used antidepressants in the U.S. in 2010, with 135.4 million prescriptions dispensed last year, according to IMS Health.
Breast cancer is the second-most common malignancy in women, after skin tumors, according to the U.S. Centers for Disease Control and Prevention in Atlanta. In 2007, the most recent year for which CDC data are available, 202,964 women were diagnosed with breast cancer and 40,598 died from it.
A study published in 2009 found that SSRIs interfered with the breast cancer medication tamoxifen, with tumors more than twice as likely to return after two years in women taking antidepressants compared with those taking tamoxifen alone. The FDA doesn’t plan to amend the drug’s label to include interactions with SSRIs, Erica Jefferson, an FDA spokeswoman, said today in an e-mail.