The Role of Selective Estrogen Receptor Modulators in the Prevention of Breast Cancer: Comparison of the Clinical Trials

Abstract

Abstract Learning Objectives After completing this course, the reader will be able to: Discuss the tamoxifen breast cancer prevention trials and the general risk-benefit profile of tamoxifen for breast cancer prevention. Compare and contrast the tamoxifen breast cancer chemoprevention trials with the ongoing raloxifene chemoprevention trials in terms of study design and baseline patient characteristics. Describe the limitations of the completed and ongoing tamoxifen and raloxifene breast cancer chemoprevention trials and the areas for future breast cancer chemoprevention research. Access and take the CME test online and receive one hour of AMA PRA category 1 credit at http://CME.TheOncologist.com The role of estrogen in the development of breast cancer is well recognized, and the use of selective estrogen receptor modulators (SERMs) to reduce breast cancer risk continues to be evaluated. Tamoxifen is the only SERM approved for the reduction of breast cancer incidence in women at high risk. This approval was based on results from the Breast Cancer Prevention Trial. Although initial results from the Royal Marsden Hospital tamoxifen trial and Italian Tamoxifen Prevention Study did not show a similar overall effect of tamoxifen, recent updates from these two trials and initial results from the International Breast Cancer Intervention Study are consistent with a risk reduction effect of tamoxifen for estrogen-receptor-positive breast cancer. Raloxifene, approved for the prevention and treatment of postmenopausal osteoporosis, is another SERM being evaluated for breast cancer risk reduction. The recently completed Continuing Outcomes Relevant to Evista® trial and the Raloxifene Use for The Heart trial, have breast cancer risk reduction as a primary end point. A third, ongoing trial, the Study of Tamoxifen and Raloxifene trial, is evaluating the relative efficacy and adverse event profile of these two agents in a population at high risk. The study populations of these raloxifene breast cancer prevention trials and the four tamoxifen prevention trials are quite diverse in terms of breast cancer risk. Completion of these trials will provide important information about the occurrence of invasive breast cancer in postmenopausal women and the efficacy of raloxifene for breast cancer risk reduction.