Do I Have To Take Tamoxifen?

by Marcelle Pick OB/GYN NP

This is one of the most common questions I am asked. I think it is because informed women now question it’s side effects. This pill, the most widely prescribed oral medication for breast cancer, has been studied in more trials than any other drug. However, the patent for Tamoxifen is running out and there are some newer hormonal blockers. Tamoxifen has an interesting history. It is not a new drug — it was synthesized back in the 70’s to be a birth control pill. It worked that way in mice, but instead increased fertility in women. Other scientists then decided to try it on advanced breast cancer patients and it did help — extending survival by many months or years. Tamoxifen is now seen as an estrogen blocker to the breasts — it inhibits estrogen from binding to cells. However in other parts of the body, the uterus, bones, ovary, it acts like an estrogen.

We now know that Tamoxifen has some negative side effects, increasing hot flashes, mood swings, and most significantly, increasing blood clots and uterine cancer. The last two are pretty rare, but significant. When Tamoxifen is used in women with more advanced breast cancer, positive nodes or metastases, the benefits exceed these risks. However, for women with earlier stages, like DCIS or very small tumors, one does need to balance the benefits with the risks. A woman should be able to have an objective discussion with her provider about the true benefits of Tamoxifen — is it 3% or 10% improvement — and then make an informed decision. Some women want to do everything, even if the benefit is small; others do not see it that way. For some women Tamoxifen is a safety net; for others it is a poison they cannot swallow.

Tamoxifen is now FDA approved for prevention of breast cancer in women with strong family histories or with atypical biopsies or LCIS. I have found that Tamoxifen is actually best tolerated by the younger women — women from the age 35 to 45. They are still having their periods and do not have any side effects. It is recommended that they take it for 5 years (using contraception, because of potential birth defects) and that the benefits last a lifetime. I have seen perimenopausal women have the most problems with Tamoxifen, as far as aggravating the symptoms of menopause and “just not feeling right.” Some women tough it out, others stop. The recommendation is to take it for 5 years only — the most benefit comes from at least 2 years. No one has tested it for, say 3 or 4 years. I often suggest that women give Tamoxifen a try for at least 3 months and keep a diary of how they feel taking it. Belief is important here and if you don’t think it is going to work, I doubt that it will.

For post menopausal women, newer drugs called aromatase inhibitors are on the market and appear to be superior to Tamoxifen. They block the conversion of estrogen from one’s fat, cholesterol or adrenal sources. Women seem to have fewer side effects, except for joint pain, with these drugs. However, they have only been studied for the last 5 years so we don’t have long term data on them. You can also ask your doctor about ovarian suppression by surgery or pills. The benefits may be equal to chemotherapy, but also have other side effects — going into sudden menopause.

Now being tested is a tamoxifen gel to be applied topically to the breasts. The hope is that it will still have its protective effects without the downside.

Hopefully in the near future we will have a better understanding of which women need which drugs.