Examining stools for colon cancer prevention: what are we really looking for?

Fecal immunochemical testing (FIT) is superior to guiac-based testing if we are looking for blood in stools, as it has better one-time colorectal cancer sensitivity and specificity and better patient acceptance. In this issue of the journal, Cai and colleagues (beginning on page 1572) and Khalid-de Bakker and colleagues (beginning on page 1563) present new information about the one-time test performance of FIT. FIT will have a growing appeal to providers and health care systems as resources for clinical preventive services shrink and as incentives to expand colorectal screening rates increase, but there are good reasons to be cautious about the temptation to organize new FIT screening programs. Colorectal screening has two potential objectives: To find cancers in an earlier, more-treatable stage and to find and remove adenomas to prevent cancers from forming in the first place. Because most adenomas, even advanced adenomas, do not bleed, tests designed to identify occult blood in the stool are better for detecting colorectal cancer, whereas direct endoscopic visualization of the colorectum is better for prevention. Even if advanced adenomas did commonly bleed, low compliance with repeat annual testing will seriously erode the benefit of FIT.