A nationwide cohort study reported that returning mailed multitarget stool DNA screening kits was associated with a 55% lower rate of subsequent colorectal cancer compared with not returning the kits. The findings connect screening participation behavior to downstream outcomes, reinforcing the role of implementation and adherence in realizing screening benefits. For health systems facing low uptake, the result supports investment in processes that convert mailed outreach into completed diagnostic-quality testing, rather than treating screening as satisfied simply by kit distribution.