Abstract
The update of the Study of Tamoxifen and Raloxifene by Vogel et al. (beginning on p. 696 in this issue of the journal) highlights the overall importance of long-term follow-up of cancer prevention trials, which need long follow-up to fully determine agent risks and benefits. Biomarkers (e.g., reduced cervical intraepithelial neoplasia 3 after human papillomavirus vaccination) can provide an early indication of efficacy but almost never replace the cancer end point in determining the ultimate utility of an agent. Long follow-up is also important to fully determine preventive benefit, as illustrated by the tamoxifen trials, where only 60% as many treated women were needed to prevent one cancer at 10 years as at approximately 5 years, the time of the early reports.