Diverticulosis and the risk of interval colorectal cancer.

BACKGROUND: Diverticulosis, a prevalent condition at screening colonoscopy, has been associated with colorectal cancers that develop after a clearing colonoscopy, or interval cancers. AIMS: To quantify the overall risk of diverticulosis in the development of interval cancers and examine this association in relevant subgroups.
METHODS: Using a linked database containing SEER tumor registry data and Medicare claims, we identified patients aged ≥69 years with colorectal cancer who underwent colonoscopy within 6 months of diagnosis. Patients with an additional colonoscopy from 36 to 6 months prior to cancer diagnosis were characterized as having interval cancers. We compared characteristics of patients with interval cancers and detected cancers according to a diagnosis of diverticulosis not associated with a colonoscopy procedure from 1991 through the date of the most recent colonoscopy in both univariate and multivariate models.
RESULTS: A previous diagnosis of diverticulosis was documented in 14,452 (26.9 %) patients with detected cancers compared to 2,905 (69.3 %) patients with interval cancers (p < 0.001); these results were consistent in multivariable analysis. Moreover, the association was found as well in the proximal colon (OR 2.88, 95 % CI 2.66, 3.12), distal colon (OR 3.56, 95 % CI 3.09, 4.11), and rectum (OR 4.07, 95 % CI 3.34, 4.95). The vast majority of diverticulosis diagnoses were without complications such as hemorrhage or diverticulitis.
CONCLUSIONS: Diverticulosis was strongly associated with interval colorectal cancers in all segments of the colon. Given its known predominance in the left colon, the findings argue against impaired visualization of lesions at colonoscopy as the only pathogenic factor.