According to a recent article published in The Lancet, results of a large clinical trial indicate that the use of Nolvadex® (tamoxifen) may reduce the risk of developing breast cancer in women who are at a high risk of developing the disease. However, side effects and deaths possibly related to Nolvadex® need to be further investigated in future clinical trials to determine the risks associated with preventive Nolvadex® use.
Since breast cancer claims the lives of approximately 40,000 women each year in the United States alone, researchers have been evaluating ways to reduce the risk or prevent the development of the disease. Some women with a family history of breast cancer are considered to be at a high risk of developing breast cancer and researchers are targeting this group of women in the evaluation of preventive therapies.
Estrogen and/or progesterone are two main female hormones and are thought to play a large role in the development of some breast cancers. Nolvadex® is a hormonal agent that blocks the effects of estrogen on a cell and reduces the growth-stimulatory processes caused by the hormone. It is approved for the treatment of hormone-positive breast cancer and is being studied as preventive therapy in women at a high risk for developing breast cancer. However, Nolvadex® is associated with side effects, including, but not limited to, thromboembolic events (clotting of the blood) and an increased incidence of endometrial (uterine) cancer.
Researchers from England and Australia conducted a clinical trial involving over 7,000 women, ages 35 to 70 years, who were at a high risk for developing breast cancer. Patients were divided into two groups: those who received Nolvadex® and those who received a placebo (inactive substitute) for five years. Approximately 50 months following initiation of therapy, breast cancer incidence was reduced by 32% in patients treated with Nolvadex® compared to patients treated with placebo. However, the incidence of thromboembolic events and death not related to breast cancer occurred in 25 patients treated with Nolvadex®, compared to only 11 patients treated with placebo.
These researchers concluded that Nolvadex® appears to reduce the risk of developing breast cancer in women who are at a high risk of developing breast cancer; however, death not related to breast cancer was increased in patients treated with Nolvadex®. The authors state that women who are at a high risk for developing thromboembolism may not be appropriate candidates for preventive Nolvadex®. Furthermore, the authors suggest that treatment with Nolvadex® should be halted during and after surgeries or periods of prolonged immobilization and appropriate antithrombotic measures should be taken. Further clinical studies are needed to definitively determine the risks and benefits of preventive therapy with Nolvadex® in women who are at a high risk for developing breast cancer. Patients with a family history of breast cancer may wish to speak with their physician about their particular risk of developing breast cancer as well as the risks and benefits of preventive therapy or participation in a clinical trial further evaluating preventive treatment strategies. Sources of information regarding ongoing clinical trials include the National Cancer Institute (cancer.gov).
Reference: International Breast Cancer Intervention Study Investigators. First results from the international breast cancer intervention study (IBIS-1): a randomized prevention trial.
The Lancet. 2002;360:813-814.