Orlistat Is Not Associated with Excess Colorectal Cancer Risk in the Short Term

The anti-obesity drug orlistat (Alli; Xenical) lowers dietary fat absorption by inhibiting intestinal lipase. Evidence in animals suggests an association between orlistat use and formation of aberrant crypt foci — a possible precursor of colorectal cancer. To assess risk for colorectal cancer following initiation of orlistat, investigators in the U.K. conducted a retrospective cohort study using data from 34,000 adult orlistat initiators and 160,000 noninitiators matched by age, sex, and body-mass index. Each initiator was matched with as many as five noninitiators; median follow-up was about 3 years.

In intent-to-treat analysis, incidence of colorectal cancer per 100,000 person-years was 53 for orlistat initiators and 50 for noninitiators. …