First Independent Assessment of Breast Cancer Risk Reduction Drugs Supports a Role for Tamoxifen Therapy

University of Pennsylvania Cancer Center
Last Modified: May 18, 1999

Atlanta, GA -- The first independent assessment of tamoxifen and raloxifene, conducted by a special American Society of Clinical Oncology (ASCO) Working Group, confirms that, based on an examination of all available literature since 1990, tamoxifen may be offered to reduce the risk of developing breast cancer for some women, but that it is still premature to recommend raloxifene outside of a clinical trial setting.

The ASCO-sponsored "technology assessment," released today, concluded that women aged 35 and older with a five-year increased risk of cancer -- a 1.7% risk or higher, or the equivalent risk of a 60 year-old woman -- may be considered tamoxifen candidates. (Approximately 29 million American women have a five-year risk of 1.7% or more.) The assessment also concluded that raloxifene has not been studied for long enough, or in a broad enough patient population, to recommend its use in this context.

The Working Group also examined survival and other health effects of the two drugs. It found that there is insufficient evidence to determine whether tamoxifen increases survival or confers a net health benefit, and is thus only appropriate for the very specific goal of lowering the risk of breast cancer. And while raloxifene increases bone mineral density, and is FDA approved for osteoporosis prevention, there is not enough data to determine whether it increases survival or reduces the risk of developing heart disease or other conditions.

"Because the pool of women who could potentially use tamoxifen is so large -- but the number who would actually benefit is relatively small -- it is very important that we understand the full range of health effects before recommending its widespread use," said Rowan T. Chlebowski, MD, Chief of the Division of Medical Oncology and Hematology at Harbor-UCLA Medical Center, and Co-Chair of the ASCO Working Group that developed the assessment.

Breast cancer is the most common cancer among women in the US, with an estimated 176,300 new cases expected in 1999. The potential breast cancer risk reduction benefits of tamoxifen and raloxifene -- agents known as Selective Estrogen Receptor Modulators (SERMs) -- are of great interest to many women. The FDA recently expanded the indication for tamoxifen, which has been used since 1978 as a treatment for breast cancer, to include breast cancer risk reduction; raloxifene, a drug approved to prevent osteoporosis in postmenopausal women, is currently being studied to determine its potential to reduce the risk of breast cancer.

"In all circumstances, the use of drugs for breast cancer risk reduction should be part of an informed decision-making process that takes the total health of a woman into account," said Deborah E. Collyar, President of PAIR: Patient Advocates in Research, and Co-Chair of the ASCO Working Group. "This assessment should be used to help facilitate communication between women at increased risk for breast cancer and their physicians."

The assessment is an analysis of all research conducted on tamoxifen and raloxifene from 1990 through 1998. It was conducted by an ASCO Working Group comprised of 23 leading experts in oncology, gynecology, epidemiology, prevention and other related disciplines. It is the first Working Group to include a patient advocate as Co-Chair, along with three additional patient advocate participants -- underscoring the importance of input from the non-medical community in broad-based recommendations.

Conclusions about the use of tamoxifen and raloxifene are based on single-agent use of these drugs. At the present time, the effect of these agents with other medications, such as hormone replacement therapy (HRT), or using them in combination or sequentially have not been adequately studied or studied at all. In addition, there is not sufficient data to support use of raloxifene for treatment of established breast cancer or to use it in combination with tamoxifen or sequentially after tamoxifen after breast cancer surgery.