Re: tamoxifen prevention of breast cancer: an instance of the fingerpost

How should we inform women at higher risk of breast cancer about tamoxifen? An approach with a decision guide

BACKGROUND

Tamoxifen has been shown to reduce the incidence of invasive breast cancer in women at higher risk. Translating these research results to clinical practice is challenging. Our objective was to develop and evaluate a decision-making guide and process that can be used in clinical practice to inform eligible women of chemoprevention with tamoxifen.

METHODS

A decision guide explaining the benefits and risks of tamoxifen was developed with input from health care professionals and two focus groups of women both with and without cancer. Following consent, 51 eligible women presenting to a multi-disciplinary diagnostic facility for breast problems were given the decision guide/questionnaire to read, fill out and return by mail. Women with further questions or wanting to take tamoxifen were encouraged to re-contact their physicians.

RESULTS

Atypia was seen in 60% of subjects. Median 5-year Gail risk was 3.7 (range 1.7-9.4). Only 6 (11.8% 95% CI = 2.9, 20.6%) women reported they would like to take tamoxifen while 6 (11.8% 95% CI = 2.9, 20.6%) remained uncertain.

CONCLUSION

We have developed a decision-making guide and process that is acceptable to providers and women to identify and inform women at higher risk of breast cancer with regard to chemoprevention with tamoxifen. Few women in this select group, when provided with a balanced decision guide, wished to pursue chemoprevention with tamoxifen.

First do no harm: extending the debate on the provision of preventive tamoxifen

The Breast Cancer Prevention Trial (BCPT-P-1) demonstrated that tamoxifen could reduce the risk of invasive breast cancer in high-risk women by 49%, but that it could also increase the risk of endometrial cancer, vascular events and cataracts. This paper provides an estimate of the net health impacts of tamoxifen administration on high-risk Canadian women with no prior history of breast cancer. The results of the BCPT-P-1 were incorporated into the breast cancer and other modules of Statistics Canada's microsimulation POpulation HEalth Model (POHEM). While the main intervention scenario conformed as closely as possible to the eligibility criteria for tamoxifen in the BCPT-P-1 protocol, 3 additional scenarios were simulated. Predicted absolute risks of breast cancer at 5 years of 1.66%, 3.32% and 4.15% were calculated for women 35 to 70 years of age. When the BCPT-P-1 results were incorporated into the simulation model, the analysis suggests no increase in life expectancy in this risk group. Tamoxifen appeared to be beneficial for women with a 5-year predicted risk of 3.32% or greater. The results of these simulations are particularly sensitive to the reduction in mortality observed in the BCPT-P-1, as well as being sensitive to other characteristics of the simulation model. Overall, the analysis raises questions about the use of tamoxifen in otherwise healthy women at high risk of breast cancer.

Chemoprevention of breast cancer

Despite a recent trend toward improvement in the U.S. breast cancer mortality rate, breast cancer incidence (182,800 new cases anticipated in 2000) and mortality figures (over 40,800 anticipated deaths) remain the highest and second highest, respectively, of all cancers in U.S. women. In 1998, the selective-estrogen-receptor-modulator (SERM) tamoxifen achieved positive results in the Breast Cancer Prevention Trial (BCPT), leading to the Food and Drug Administration (FDA) approval of tamoxifen for risk reduction in women at high risk of breast cancer (the historic first FDA approval of a cancer preventive agent). This brought about a paradigm shift in new approaches for controlling breast cancer toward pharmacologic preventive regimens, called chemoprevention. This paper presents a comprehensive clinical review of breast cancer prevention study, highlighting issues of the extensive study of tamoxifen. These issues include the record of primary tamoxifen results in several breast-cancer risk-reduction settings (primary, adjuvant, and ductal carcinoma in situ [DCIS]); critical secondary BCPT risk-benefit findings (including quality of life issues) and their effects on counseling patients on use of tamoxifen for prevention; ethic minorities; optimal tamoxifen dose/duration; and potential impact on mortality and other issues involved with potential net benefit to society. Other breast-cancer chemoprevention issues reviewed here include women at high genetic risk (especially BRCA1 mutation carriers); raloxifene in breast cancer prevention; other SERMs; SERM resistance; and new agents and combinations currently in development. Very recent developments involving PPAR-gamma ligands, COX-2 inhibitors, and RXR-ligands are discussed in the section on new drug development.