Commonly Asked Questions About Tamoxifen
1. What is tamoxifen?
Tamoxifen is a drug taken by mouth as a pill. It has been used for 25 years to treat patients with advanced breast cancer. Since 1985, it has also been recommended in the United States for adjuvant, or additional therapy, following surgery and/or radiation for early-stage breast cancer. Tamoxifen works against breast cancer, in part, by interfering with the activity of estrogen, a female hormone that promotes the growth of breast cancer cells. For this reason, tamoxifen is often called an "anti-estrogen." In treatment, the drug slows or stops the growth of these cancer cells.
2. Why was tamoxifen tested to prevent breast cancer?
Research has shown that taking tamoxifen as adjuvant therapy for breast cancer not only helps prevent the original breast cancer from returning, but also helps to prevent the development of new cancers in the opposite breast. Researchers believed that tamoxifen might have a similar beneficial effect for women at increased risk of breast cancer. While tamoxifen acts against the effects of estrogen in breast tissue, it acts like estrogen in other body systems. Tamoxifen's estrogen-like effects include the lowering of blood cholesterol and the slowing of bone loss.
3. What factors were used to determine increased risk of breast cancer for the participants in the study, ages 35-59?
To enroll in the study, women ages 35-59 needed to have a risk of developing breast cancer within the next five years that was equal to or greater than the risk for 60-year-old women. The increased risk was determined in one of two ways: Women diagnosed as having lobular carcinoma in situ, a condition that is not cancer but indicates an increased chance of developing invasive breast cancer, were eligible based on that diagnosis alone. The risk for other women was determined by a computer calculation based on the following factors:
· number of first-degree relatives (mother, daughters, or sisters) who had been diagnosed as having breast cancer;
· whether a woman had any children, and her age at her first delivery;
· the number of times a woman had breast lumps biopsied, especially if the tissue was shown to have a condition know as atypical hyperplasia;
· the woman's age at her first menstrual period.
4. What are the initial results of the study?
At this point (Jan. 31, 1998), women on the trial have been followed on the study for about four years. Results show 45% fewer diagnoses of invasive breast cancer in women who were randomized to take tamoxifen compared to women who took a placebo.
5. What will the participants do now?
All participants are being asked to continue with their follow-up examinations. Women who have been randomized to the tamoxifen group who have not completed five years of tamoxifen therapy will have the opportunity to continue on therapy. Postmenopausal women who had been taking the placebo are being invited to participate in an upcoming trial that will compare tamoxifen to a different drug that could have similar breast cancer prevention properties, but might be associated with fewer adverse effects. Women of any age on placebo also have the option of seeking tamoxifen from their private health care providers.
6. Would it be beneficial for women to take tamoxifen for more than five years?
Not necessarily. Results of another National Surgical Adjuvant Breast and Bowel Project study in which women with early stage breast cancer took tamoxifen for five years vs. 10 years showed no greater benefits from the longer duration and showed a trend toward more adverse effects.
7. Should women who are not at a demonstrated increased risk of breast cancer consider taking tamoxifen?
This question has not been studied. At this time, there is no evidence that tamoxifen is beneficial for women who do not have an increased risk of breast cancer.
8. How much does a standard dose of tamoxifen cost?
A month's supply costs about $80 to $100.
9. What were any adverse side effects?
Tamoxifen did increase the women's chances of three rare, but serious, health problems: endometrial cancer, pulmonary embolism (blood clot in the lung), and deep vein thrombosis (blood clots in major veins).
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