Re: Tamoxifen Prevention of Breast Cancer: an Instance of the Fingerpost

Extract

In their commentary on tamoxifen, Lippman and Brown [(1), p. 1813] cite figures from Fisher (2) and state that “these figures demonstrate that tamoxifen prevention potentially could impart a substantial net benefit to the public health.” In light of the article presented by Gail et al. (3) in the same issue of the Journal and some of our own calculations given below, we wish to offer a different perspective.

According to Fisher's cited commentary (2), approximately 29 million women in the United States would meet the eligibility criteria for the Breast Cancer Prevention Trial (BCPT) (4), and in this group of 29 million, 1.4 million cases of breast cancer might be expected during the course of 5 years, of which 700000 would potentially be prevented by prophylactic use of tamoxifen. First, there are not 1.4 million cases of breast cancer in the entire population of U.S. women over a 5-year period. For the past 5 years, there have been between 175000 and 185000 cases of breast cancer per year (5). Second, not all breast cancer cases are going to occur among women eligible for tamoxifen chemoprevention. Women were eligible for the BCPT if they fell into one of the following categories (4): aged 35–59 years with a 5-year risk of at least 1.67% (the 5-year risk of the “average” 60-year-old U.S. woman) according to the model of Gail et al. (6), age greater than or equal to 60 years, or history of lobular carcinoma in situ.