Chemoprevention of breast cancer - with special interest of tamoxifen

Abstract

The adjuvant use of tamoxifen confers a survival advantage for patients with node-positive and node-negative breast cancer and demonstrated benefit when used alone or in combination with chemotherapy to treat advanced breast cancer.Tamoxifen prevents induced mammary cancer in rats, decreases the contralateral breast cancer incidence in humans, and its safety record in clinical practice is excellent. This finding led to the concept that the drug might play role in breast cancer prevention. In 1986 at the Royal Marsden Hospital a small pilot study was started, which would serve as a feasibility assessment for a larger trial to determine if tamoxifen prevents breast cancer. The trial shows no effect, because the study is too small for accurate results. Similarly, in another tamoxifen prevention study performed in Italy, the incidence of breast cancer did not differ between groups of tamoxifen and placebo. The negative finding of the study is readily explained by the relatively low risk of breast cancer development in the study population, the high drop-out rate and the small number of women who completed 5 years of treatment. In the NSABP P-1 prevention trial tamoxifen reduced the risk of invasive breast cancer by 49% and of noninvasive breast cancer by 50% in the increased risk population of 13.388 healthy women. The article summarizes the recent theoretical and practical data of the chemoprevention of breast cancer.