Scottish researchers have found that women get the maximum benefit fro No Need for Women to Take Tamoxifen Longer Than Five Years, Study Finds (dateline March 27, 2001) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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No Need for Women to Take Tamoxifen Longer Than Five Years, Study Finds (dateline March 27, 2001)


Scottish researchers have found that women get the maximum benefit from the drug tamoxifen (brand name, Nolvadex) by taking it for a period of five years—no longer, no shorter. Tamoxifen has been used for over 20 years to treat advanced breast cancer, and in 1998, it became the first drug approved by the U.S. Food and Drug Administration (FDA) to help prevent breast cancer in women at high risk of the disease. The study revealed that taking tamoxifen for five years immediately after other breast cancer treatments (such as surgery and radiation) helps reduce the chance of a cancer recurrence, but the benefit does not continue beyond five years of use.

In the study, Dr. Helen Stewart, formerly of the Scottish Cancer Trials Office in Edinburgh, Scotland, and her colleagues followed 1,300 breast cancer patients for a period of 15 years. Approximately half of the patients were given tamoxifen immediately after mastectomy (surgical breast removal) and radiation therapy while the other half of the patients were given tamoxifen only after they experienced a recurrence of breast cancer. Some of the patients took tamoxifen indefinitely while others were told to stop taking tamoxifen after certain periods of time.

The results of the study showed that the women treated with tamoxifen immediately after mastectomy and radiation survived longer and were less likely to experience a recurrence of breast cancer or die from the disease than the women who were treated with tamoxifen only after experiencing a recurrence of breast cancer. For example, approximately 13% fewer women died from breast cancer if they took tamoxifen following mastectomy and radiation than if they waited to begin tamoxifen until after a breast cancer recurrence.

According to Dr. Stewart and her colleagues, their data suggest that there is no additional beneficial effect of tamoxifen after five years of use. In the study, women who used tamoxifen for five and a half years were at a slightly higher than average risk for endometrial cancer (cancer of the uterine lining), which the researchers say may be associated with long-term tamoxifen use. However, previous research has shown that even taking tamoxifen for a shorter amount of time can still increase the risk of endometrial cancer: approximately 2 out of 1,000 women on tamoxifen develop endometrial cancer.

Previous studies have also shown that taking tamoxifen for longer than five years may actually reverse its beneficial effects. Because tamoxifen may begin to mimic estrogen in breast cells with prolonged use, it may actually stimulate the growth of cancers after a period of five years. Further research still needs to be conducted to better understand the risks of taking tamoxifen for longer than five years. However, a large amount of data show that women can receive the most benefit from tamoxifen by taking it for a full five years. Preliminary data also suggests that tamoxifen can help protect against heart disease in both women and men.

Tamoxifen may be prescribed to:

  • Patients with invasive breast cancer (typically in combination with chemotherapy or other treatment)
  • Patients with early stage breast cancers (in combination with other treatments such as surgery, radiation, etc.)
  • Patients at high risk of developing breast cancer (as determined by family history of breast cancer, etc.)

While tamoxifen can be effective at treating or preventing breast cancer, side effects may occur with use. The most common side effect of tamoxifen is a higher occurrence of hot flashes. Less commonly, tamoxifen may be associated with serious conditions such as endometrial cancer, deep vein thrombosis (blood clots in legs), pulmonary embolism (blood clots in lungs), or stroke.  Women who are considering tamoxifen should discuss the benefits and risks of the drug prior to use.

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