Tamoxifen

On the fifth of April, when I had my last Herceptin Dr. K talked to me about the oral drug tamoxifen. I had known for a long time that this was coming. I really struggled with taking it and actually avoided picking up the drug for a while. There are some side effects to the drug that I would prefer to avoid. I have talked to people who have taken it. I have talked to a couple of women whose Doctor says that the risks don’t outweigh the positives. Below is information from the National Cancer Instiute about Tamoxifen.


1. Tamoxifen (Nolvadex®) is a drug, taken orally as a tablet, which interferes with the activity of estrogen, a female hormone. Estrogen can promote the development of cancer in the breast. Tamoxifen is approved by the U.S. Food and Drug Administration (FDA) for the prevention of breast cancer and for the treatment of breast cancer, as well as other types of cancer.

Tamoxifen has been used for more than 30 years to treat breast cancer in women and men. Tamoxifen is used to treat patients with early-stage breast cancer, as well as those with metastatic breast cancer (cancer that has spread to other parts of the body). As adjuvant therapy (treatment given after the primary treatment to increase the chances of a cure), tamoxifen helps prevent the original breast cancer from returning and also helps prevent the development of new cancers in the other breast. As treatment for metastatic breast cancer, the drug slows or stops the growth of cancer cells that are present in the body.

Tamoxifen has been used for almost 10 years to reduce the risk of breast cancer in women who are at increased risk of developing breast cancer. Tamoxifen is also used to treat women with ductal carcinoma in situ (DCIS), a noninvasive condition that sometimes leads to invasive breast cancer.

How does tamoxifen work?

Estrogen can promote the growth of breast cancer cells. Some breast cancers are classified as estrogen receptor-positive (also known as hormone sensitive), which means that they have a protein to which estrogen will bind. These breast cancer cells need estrogen to grow. Tamoxifen works against the effects of estrogen on these cells. It is often called an antiestrogen or a SERM (Selective Estrogen Receptor Modulator).

Studies have shown that tamoxifen is only effective in treating estrogen receptor-positive breast cancers. Therefore, the tumor’s hormone receptor status should be determined before deciding on treatment options for breast cancer.

Although tamoxifen acts against the effects of estrogen in breast tissue, it acts like estrogen in other tissue. This means that women who take tamoxifen may derive many of the beneficial effects of menopausal estrogen replacement therapy, such as a decreased risk of osteoporosis.

What are some of the more common side effects of tamoxifen?

The known, serious side effects of tamoxifen are blood clots, strokes, uterine cancer, and cataracts (see Questions 5–8). Other side effects of tamoxifen are similar to the symptoms of menopause. The most common side effects are hot flashes and vaginal discharge. Some women experience irregular menstrual periods, headaches, fatigue, nausea and/or vomiting, vaginal dryness or itching, irritation of the skin around the vagina, and skin rash. As with menopause, not all women who take tamoxifen have these symptoms. Men who take tamoxifen may experience headaches, nausea and/or vomiting, skin rash, impotence, or a decrease in sexual interest.

Does tamoxifen cause cancers of the uterus?

Tamoxifen increases the risk of two types of cancer that can develop in the uterus: endometrial cancer, which arises in the lining of the uterus, and uterine sarcoma, which arises in the muscular wall of the uterus. Like all cancers, endometrial cancer and uterine sarcoma are potentially life-threatening. Women who have had a hysterectomy (surgery to remove the uterus) and are taking tamoxifen are not at increased risk for these cancers.

Endometrial Cancer

Studies have found the risk of developing endometrial cancer to be about 2 cases per 1,000 women taking tamoxifen each year compared with 1 case per 1,000 women taking placebo (1, 2). Most of the endometrial cancers that have occurred in women taking tamoxifen have been found in the early stages, and treatment has usually been effective. However, for some breast cancer patients who developed endometrial cancer while taking tamoxifen, the disease was life-threatening.

Uterine Sarcoma

Studies have found the risk of developing uterine sarcoma to be slightly higher in women taking tamoxifen compared with women taking placebo. However, it was less than 1 case per 1,000 women per year in both groups (1, 2). Research to date indicates that uterine sarcoma is more likely to be diagnosed at later stages than endometrial cancer, and may therefore be harder to control and more life-threatening than endometrial cancer.

Abnormal vaginal bleeding and lower abdominal (pelvic) pain are symptoms of cancers of the uterus. Women who are taking tamoxifen should talk with their doctor about having regular pelvic examinations and should be checked promptly if they have any abnormal vaginal bleeding or pelvic pain between scheduled exams.