Increased frequency of serrated aberrant crypt foci among smokers

The American College of Gastroenterology has published guidelines recently that suggest that smokers with a history of >20 pack years may need screening for colorectal cancer (CRC) at an earlier age than non-smokers. Aberrant crypt foci (ACF) may represent important precursors for colorectal neoplasms and potential surrogate biomarkers. Clarifying the role of ACF in relation to known CRC risk factors such as smoking may have important implications for screening as well as our understanding of tobacco use and colorectal carcinogenesis. Our goal was to examine whether smoking at least 20 pack years was associated with an increased frequency of ACF.

We gathered detailed smoking history, personal and family history of CRC, and other epidemiologic data (age, gender, height, weight, ethnicity, and medication use) from 125 patients undergoing routine screening or surveillance colonoscopy. We used a magnifying colonoscope (Olympus Close Focus Colonoscope XCF-Q160ALE, Olympus Corporation, Tokyo, Japan) and examined the distal 20 cm section of colon after staining with 0.5% methylene blue. ACF were counted and characterized histologically. Hyperplastic ACF were further characterized as either serrated or non-serrated.

Smoking at least 20 pack years was associated with an increased likelihood (adjusted odds ratio (OR)=3.45; 95% confidence interval (CI)=1.93-6.18) of having more than the median number of ACF (> or = 15) compared with non-smokers. Similarly, patients with a personal history of advanced neoplasia were more likely (adjusted OR=3.42; 95% CI=1.01-11.67) to have a greater than median number of ACF compared with patients without this diagnosis. Smokers were more likely than non-smokers to have serrated ACF (P=0.002).

Smoking at least 20 pack years seems to be associated with increased number of ACF in the rectum and distal sigmoid, especially those with serrated histology. Our data support ACG guidelines for earlier screening for CRC among smokers and add to our understanding of how colorectal carcinogenesis is related to tobacco use.