February 14, 2002
For Immediate Release
Heavy exposure to some tricyclic antidepressants associated with elevated risk of breast cancer
Toronto - Women prescribed some of the tricyclic antidepressants (TCA) to treat depression show an elevated risk of breast cancer 11- 15 years later, suggests a paper published in the British Journal of Cancer.
Dr. Colin Sharpe and his research team at Montreal's Sir Mortimer B. Davis-Jewish General Hospital conducted a case-control study among women 35 years or older with no history of cancer since 1970, who were enrolled in the Saskatchewan Prescription Drug Plan from 1981 - 1995.
The study examined women's prescription records of exposure to 10 different tricyclic antidepressants over various time periods preceding the diagnosis of breast cancer. ”Since cancer is a disease that develops over long periods of time,” says Dr. Sharpe, ”the effects of exposure to potentially genetically toxic substances during different periods of time should be studied separately to determine their effects on cancer development.”
Heavy exposure to TCAs was associated with an increased risk of breast cancer 11-15 years later. ”The greater than 10 year delay between TCA exposure and the increase in the incidence rate of breast cancer suggested to us that the drugs might be acting as tumour initiators,” he adds.
Dr. Sharpe investigated further, building on an earlier discovery of a Swiss team, who in experiments involving fruit flies, had found six of the TCA drugs to be genotoxic (i.e. toxic to DNA, leading to mutations). Use of those six TCA genotoxic drugs was found to be associated with an increased risk of breast cancer. Use of the four TCAs that the scientists found were not genotoxic in fruit flies was not associated with an increased risk of breast cancer. Dr. Sharpe found that the incidence rate of breast cancer in women taking genotoxic TCAs was about two times higher than the corresponding rate among women who were taking nongenotoxic TCAs.
The six TCAs that were shown to be genotoxic in fruit flies and associated with an increased risk of breast cancer in women were: amoxapine, clomipramine, desipramine, doxepin, imipramine, and trimipramine. The four TCAs that were shown to be nongenotoxic in fruit flies and not associated with an increased risk of breast cancer were: amitriptyline, maprotiline, nortriptyline, and protriptyline.
Dr. Sharpe says that the results of his team's study corroborate the recommendations of the scientists in Switzerland, who suggested that physicians should consider genotoxicity data when prescribing medications. He suggests that physicians should avoid prescribing the genotoxic TCAs and should prescribe the nongenotoxic TCAs instead. The team will be carrying out additional case-control studies to determine if the use of the genotoxic TCAs is associated with the development of any other types of cancer, including cancers in men as well.
”Although this study suggests there may be an increased risk of breast cancer, a woman who is taking antidepressant medication should not panic. The risks and benefits of antidepressant medication have to be balanced, and should always be discussed with the woman's physician,” advises Dr. Marilyn Schneider, executive director of the Canadian Breast Cancer Research Initiative. ”All women - not just those who have taken antidepressants - should take responsibility for their own breast health. All women should undergo regular mammograms, as appropriate, as well as conduct breast self examination and receive clinical breast examination by their physician”
Dr. Sharpe's paper is based on the study entitled ”Case-control study of the effect of non-steroidal anti-inflammatory and anti-depressants on the risk of breast cancer,” led by Dr. Jean-Paul Collet of the Lady Davis Institute in Montreal and funded by the Canadian Breast Cancer Research Initiative.
The paper ”The effects of tricyclic antidepressants on breast cancer risk” was published in the British Journal of Cancer, volume 86, pages 92-97, on January 7, 2002.
The Canadian Breast Cancer Research Initiative is Canada's primary funder of breast cancer research. As a unique partnership of groups from the public, private and non-profit sectors, the Initiative is committed to reducing the incidence of breast cancer, increasing survival, and enhancing the lives of those affected by the disease. CBCRI partners include the Avon Flame Foundation, the Canadian Breast Cancer Foundation, the Canadian Breast Cancer Network, the Canadian Cancer Society, the Canadian Institutes of Health Research, Health Canada and the National Cancer Institute of Canada.
For more information visit the web site: http://www.breast.cancer.ca/
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