Tamoxifen Warning Clarified

Cancer Care Nova Scotia today, Dec. 4, clarified a recent Health Canada warning about the side effects of the breast cancer drug Tamoxifen. The warning applies only to women not diagnosed with breast cancer, who may be taking the drug as a preventive measure. The drug has never been approved for use in Canada as a preventive drug for women who do not have breast cancer.

The warning does not apply to women who are on Tamoxifen to reduce the risk of recurrence of breast cancer, diagnosed by a lumpectomy or mastectomy, nor does it apply to those who are taking it to treat advanced disease. Health Canada specifies that "the benefits of using Tamoxifen in the treatment of breast cancer outweighs the risks of side effects for the majority of patients."

"Breast cancer patients have enough to deal with, without adding unnecessary anxiety and worry to an already stressful situation," said Dr. Daniel Rayson, medical oncologist, Capital Health Cancer Care Program and chair of Cancer Care Nova Scotia's Breast Cancer Site Team. "Our team wants to reassure women who are taking Tamoxifen to decrease the risk of recurrent breast cancer that this recent warning does not change their treatment recommendation. However, women who are worried should discuss their concerns with their cancer specialist or family doctor."

Side effects of Tamoxifen may include hot flashes, vaginal discharge and dryness. Women on Tamoxifen may also develop cataracts at a faster rate and have a one per cent greater risk of blood clots, in addition to a very slight risk of uterine cancer, compared with women not on the medication.

Tamoxifen is the most commonly prescribed hormonal therapy for prevention of breast cancer recurrence. It has been in use since the 1970s and has been shown to lead to a 35 to 50 per cent reduction in the risk of breast cancer recurrence if the cancer has hormone (estrogen and/or progesterone) receptors.

"It's important for women to know that the Health Canada warning is not based on any new data," said Dr. Rayson. "The Health Canada advisory resulted from a review of a U.S. study on breast cancer prevention by the National Surgical Adjuvant Breast and Bowel Project. The side effects described are part of the risk/benefit discussion every woman should have with their cancer specialist before deciding on a course of treatment."

The Breast Cancer Site Team is one of 13 cancer site teams established by Cancer Care Nova Scotia to develop clinical practice guidelines and standards of care. The guidelines and standards are to ensure that all Nova Scotians receive treatments that are based on the most up-to-date information.

Cancer Care Nova Scotia is a program of the Department of Health, created to reduce the burden of cancer on individuals, families and the health care system through prevention, screening, education and research.