Adjuvant endocrine therapy in hormone receptor-positive postmenopausal breast cancer: evolution of NCCN, ASCO, and St Gallen recommendations.

Endocrine therapy has a firm role in adjuvant treatment of women with hormone receptor-positive invasive breast cancer. Until recently, tamoxifen was the most commonly used adjuvant endocrine therapy in premenopausal and postmenopausal women. Several randomized clinical trials have studied the third-generation selective aromatase inhibitors (AIs) (anastrozole, letrozole, and exemestane) as adjuvant endocrine therapy in postmenopausal women. These studies compared therapy with an AI alone versus tamoxifen alone; 2 to 3 years of tamoxifen followed by switching to an AI versus continuation of tamoxifen; or extended therapy with an AI after approximately 5 years of tamoxifen therapy. No statistically significant differences in overall survival were observed. A single trial using extended treatment with an adjuvant AI suggests a small, statistically significant survival advantage in women with axillary lymph node-positive disease while showing no statistically significant decrease in survival with the use of an AI. The toxicities of the AIs are generally acceptable, with fewer endometrial cancers, gynecologic complaints, and thromboembolic events, but more bone fractures and arthralgias compared with tamoxifen alone. Three widely disseminated treatment guidelines, the National Comprehensive Cancer Network Breast Cancer Clinical Practice Guidelines in Oncology, the American Society of Clinical Oncology Technology Assessment on the Use of Aromatase Inhibitors, and the St Gallen International Expert Consensus on the Primary Therapy of Early Breast Cancer, now incorporate AIs in the adjuvant therapy of postmenopausal women with estrogen receptor-positive breast cancer.

Developing a SERM: stringent preclinical selection criteria leading to an acceptable candidate (WAY-140424) for clinical evaluation.

Estrogens are represented by a diverse group of compounds. Within this large family of molecules are tissue-selective estrogens that have been classified as selective estrogen receptor modulators (SERMs). These compounds are characterized by the fact that they exhibit both estrogen agonist and antagonist activity dependent upon the gene promoter and target tissue being examined. SERMs have been intensively studied over the past decade, especially since one, raloxifene, has been approved for the prevention and treatment of postmenopausal osteoporosis. While not a replacement for hormone replacement therapy (HRT), raloxifene can be an alternative to it and other treatments for osteoporosis. The ideal SERM would provide the positive benefits associated with HRT without the uterine and breast stimulation. Raloxifene does achieve some of the benefits of HRT, specifically on the skeleton and lipid metabolism with no apparent uterine effects, and a potential decreased risk of developing breast cancer associated with raloxifene therapy. However, there are a number of parameters that can be improved. A number of SERMs have been evaluated only to fail in development due to, for the most part, uterine safety issues. In order to develop an improved SERM, a stringent screening process was designed to select compounds that did not stimulate the uterus or breast. At the same time, these new compounds would have a positive impact on the skeleton and lipid metabolism with the additional improvement (over raloxifene) of a neutral effect on hot flashes. Under these strict conditions, WAY-140424 was developed and, to date, the preclinical pharmacology data have accurately predicted the clinical response demonstrated in phase I and II trials.

Tamoxifen for the reduction in the incidence of breast cancer in women at high risk for breast cancer.

Recent legislation, including the Prescription Drug User Fee Act (1992) and the FDA Modernization Act (FDAMA) (1997), has provided an environment in which new drug applications (NDA) can be efficiently reviewed, resulting in rapid access to new drugs or to new uses for approved drugs by the public. The recent submission of a supplemental NDA for tamoxifen for the reduction in the incidence of breast cancer in women at high risk for breast cancer is an excellent example of the application of this legislation. First, the application received expedited but thorough multidisciplinary and interdivisional review by the FDA. Second, it required collaboration between the manufacturer (AstraZeneca Pharmaceuticals), the National Surgical Adjuvant Breast and Bowel Project (NSABP), the National Cancer Institute (NCI), and the FDA. This process worked well and demonstrated that cooperative group data can be used effectively to support an application. Third, a single large adequate and well-controlled trial was sufficient to support the effectiveness of tamoxifen for this indication. The quantity of evidence required to support approval has been discussed in FDA guidances ("Providing Clinical Evidence of Effectiveness for Human Drug and Biological Products") and is part of FDAMA.

Conclusions: Considerations regarding SERMs.

The "considerations" addressed in this section consist of a number of thought-provoking issues and unresolved questions that emerge from the papers in this volume. The evidence for tamoxifen carcinogenicity in animal models and, to a more restricted extent, in humans has led some investigators to question whether SERMs are ready or appropriate for clinical testing--specifically, in a disease prevention setting involving healthy but high-risk individuals. There is, however, inconsistency in both efficacy and toxicity--specifically, carcinogenicity--between animal models and humans, leading others to question the value of basing the decision to proceed with clinical studies on preclinical results in animals. Although the molecular basis for SERM action is rapidly being clarified, the cellular activity of these agents is still elusive. We discuss the view that the efficacy of tamoxifen in breast cancer is based on its treatment of "occult cancers," or small collections of cancer cells that are not clinically apparent, not only in the context of prevention but also in the treatment setting. As part of our approach that assumes estrogen activity to be the foundation upon which SERM development is being modeled, we discuss the inconsistency between the epidemiologic data and prospective randomized data with respect to the relationship between estrogen use and cardiovascular disease. The need to validate surrogate markers of SERM action is discussed in relation to bone but is clearly relevant to all disease sites. The semantics used in describing SERM action as agonistic or antagonistic in relation to estrogen at various target sites has been inconsistent, especially in the clinical context. We attempt to dissect out some of the inconsistencies in semantics in the hope that this will contribute to improved communication of data resulting from SERM research. In the clinical arena, we begin with the premise that the large, simple randomized trial offers the optimal design for the testing of SERMs. In view of limited resources, however, we counter this position with alternative, if less desirable, approaches to the clinical format for SERM testing. Finally, we explore the process by which statistically meaningful results from clinical trials are extrapolated into the specific drug indications that apply to clinical practice.