Problematic End Points in a Keratinocyte Carcinoma Chemoprevention Trial

To the Editor Treatment with topical fluorouracil, 5%, compared with placebo reduced risk of surgically treated squamous cell carcinoma (SCC) and Mohs surgery for keratinocyte carcinoma (KC) for 1 year, according to a randomized clinical trial (RCT) report. However, because neither of these outcomes was prespecified, these findings should be interpreted very cautiously and should not sway clinical practice.