Aspirin Prevention of Colorectal Cancer: More or Less?

The concept of cancer chemoprevention is tantalizing. If we had a pill that could prevent cancer, we might escape the need for potentially disfiguring surgery or toxic chemotherapy. If the pill were familiar, cheap, and readily available, so much the better. In this issue, Chan and colleagues (1) provide additional evidence that we may actually have such an agent for colorectal cancer. Its identity? Aspirin.

We first recognized that aspirin might decrease the risk for colorectal cancer more than 15 years ago (2). Since that time, a large number of retrospective and prospective studies have shown that regular aspirin users are less likely than nonusers to develop colorectal cancer or its precursor, adenomatous polyps (3, 4). The studies are remarkably consistent—virtually all demonstrate a protective effect of aspirin. In addition, we now have even stronger evidence: Randomized trials in which short-term use of a single daily aspirin reduced the risk for adenomas (5-7).

This issue contains an analysis of the dose and duration of aspirin necessary to prevent colorectal adenomas (1). Chan and colleagues obtained detailed information on aspirin use from a large cohort of nurses who were followed prospectively. The findings are unambiguous. Women who used …