Tamoxifen and Cancer Prevention

Dear Dr. B: Is there a pill to prevent breast cancer? Yours: Ms. Worried.

Dear Ms. Worried: There is no straight answer to this question. Studies have shown that, in some women, tamoxifen can prevent breast cancer.

Recently, an article was published on this subject in the Canadian Medical Association Journal. It is a joint guideline from the Canadian Task Force on Preventive Health Care and the Canadian Breast Cancer Initiative’s Steering Committee on Clinical Practice Guidelines for the Care and Treatment of Breast Cancer.

The objective of the guideline is to assist women and their physicians in making decisions regarding the prevention of breast cancer with tamoxifen and raloxifene.

Raloxifene is a drug used for prevention and treatment of osteoporosis in
post-menopausal women. Current evidence does not support the use of raloxifene for prevention of breast cancer.

Tamoxifen is a drug used for certain categories of women who have had breast cancer. It has shown to reduce the recurrence of cancer in the same breast, reduce the occurrence of new breast cancer in the other breast, and reduce the risk breast cancer spreading to other parts of the body (metastasis).

Tamoxifen has been found to be effective in preventing breast cancer. On that basis the Task Force has made recommendation in the use of Tamoxifen for prevention of breast cancer.

How do I know tamoxifen will help me prevent breast cancer?

First, you need to determine your risk. This is not easy. You have to go on the internet and check the Gail risk assessment index. This is a model used to estimate an individual woman’s risk of breast cancer.

The index uses a series of risk factors (age, age at first period, age at first live birth, number of breast biopsies, family history and ethnic origin) to calculate a “baseline risk.” The article says that the Breast Cancer Risk Assessment Tool, which is based on the Gail index, is available online: http://bcra.nci.nih.gov/brc. This will calculate percentage risk for you.

Once you have done that, then check the following recommendations to see if they apply to you:

1. Women at low or normal risk of breast cancer (Gail risk assessment index less than 1.66 percent at 5 years): There is fair amount of evidence to recommend against the use of tamoxifen in this group.

2. Women at higher risk of breast cancer (Gail index equal to or more than 1.66 percent at 5 years): Evidence supports counselling women in this group on the potential benefits and harms of breast cancer prevention with tamoxifen.

Examples of women in the second group would be – two first-degree relatives with breast cancer, a history of breast biopsy showing lobular carcinoma-in-situ, or atypical hyperplasia. Tamoxifen reduces the risk of breast cancer by 50 percent or in atypical hyperplasia by 86 percent.

Use of tamoxifen is not without side effects like stroke, blood clots in the lung or leg veins, cancer of the uterus, hot flashes and vaginal dryness. The article says that the side effects increase with a woman’s age.

So, Ms Worried, tamoxifen will do the trick for you if you are the right candidate. And remember, the benefits are not without side effects. “The benefit of protection against breast cancer is more likely to outweigh the risks on women aged 35 to 50 years”, says the Canadian Task Forces’ guideline.

Good luck, Ms. Worried.

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