Compliance with the study treatments and procedures was generally
good. Overall pill-taking compliance (expressed as the percentage
of expected number of study pills taken) tended to be
slightly higher in the any-dose aspirin group than in the placebo
group ( Table 3 ). Among the four studies, mean pill-taking compliance
ranged from approximately 69% to approximately 92%. At
least 81% of participants in each of the studies and at least 90% of
the participants in three studies (AFPPS, ukCAP, and APACC)
had at least one follow-up examination ( Supplementary Table 1 ,
available online). (The early termination of CALGB 9270 contributed
to the lower percentage of participants with colonoscopic
follow-up in that study.) In total, 2698 participants underwent
colonoscopic follow-up. The remaining 269 participants were