Trevor J. Powles, CBE, PhD, FRCP

The paper by Vogel is an interesting personal review of the use of selective estrogen-receptor modulators (SERMs) to prevent breast cancer, raising many important issues and concerns related to this controversial topic.

Twenty years ago, antiestrogen therapy with tamoxifen played only a secondary role in breast cancer care. All hopes to cure metastatic breast cancer were still pinned on either the discovery of new cytotoxic drugs or a dose-dense combination of available cytotoxic drugs with bone marrow transplantation. A similar strategy with combination chemotherapy was employed as an adjuvant for primary breast cancer. Simply stated, the goal was to kill the cancer with nonspecific cytotoxic drugs while keeping the patient alive with supportive care. However, medical research does not travel in straight lines, and an alternative approach emerged to solve the problem of controlling tumor growth with minimal side effects: targeted therapy. The approach of using long-term antihormone therapy to control early-stage breast cancer growth would revolutionize cancer care by targeting the tumor estrogen receptor (ER). The success of the strategy would contribute to a decrease in the national mortality figures for breast cancer. More importantly, translational research that targeted the tumor ER with a range of new antiestrogenic drugs would presage the current fashion of blocking survival pathways for the tumor by developing novel targeted treatments. But a surprise was in store when the pharmacology of "antiestrogens" was studied in detail: The nonsteroidal "antiestrogens" are selective ER modulators—ie, they are antiestrogens in the breast, estrogens in the bone—and they lower circulating cholesterol levels. This knowledge would establish a practical approach to breast cancer chemoprevention for women at high risk (tamoxifen) and low risk (raloxifene).

It is nearly 30 years since the start of clinical trials of adjuvant chemotherapy in patients with operable breast cancer.[1] The rationale for using adjuvant chemotherapy at that time was that surgery and radiotherapy could only control local disease and cure patients who did not already have metastases. Chemotherapy could be used in patients with a poor prognosis to treat undetected micrometastatic disease and thereby reduce the risk of metastatic relapse and death from breast cancer.

Various ongoing double-blind clinical trials are evaluating the use of tamoxifen (Nolvadex) as chemoprevention for breast cancer. A total of over 24,000 healthy women have been randomized to these trials, and it should be possible, by the year 2000, to detect any preventive effect of tamoxifen in healthy women. Furthermore, with the large numbers of women involved, it should be possible to evaluate prevention in subgroups of participants according to risk of the disease, particularly those women carrying high-risk genes, such as BRCA1 and BRCA2.