For a paper published in Disease of the Colon & Rectum, Gregory S. Cooper, MD, and colleagues aimed to describe the incidence of first-ever diverticulitis and prevalence of first-ever, post-diverticulitis colorectal cancer (CRC) in the United States. “Our objective was to determine if the incidence of CRC is higher than expected in this situation, which could suggest that an undiagnosed cancer may have been misdiagnosed as diverticulitis,” Dr. Cooper explains. “Although professional society guidelines typically recommend colonoscopy after a patient recovers from diverticulitis in order to exclude malignancy, data to support this practice are limited.” He adds that the prevalence of cancer in this scenario ranges from 0.5% to 7.4%.

For a retrospective cohort study, the researchers queried a national database containing data from 26 major integrated healthcare systems in the US. They identified an aggregated patient cohort aged 18 and older with a diagnosis of first-ever diverticulitis from February 2015 to February 2020, followed by first-ever CRC diagnosis at least 1 day after, and within 1 year of, diverticulitis.

Double the Incidence of Cancer in the General Population

Among nearly 31.8 million individuals, the study team found the incidence of first-ever acute diverticulitis to be 2.9%, with the infection more common in males, seniors, and Caucasians—demographics that are generally consistent with prior studies. The majority (92.3%) of post-diverticulitis CRC was diagnosed within the first 6 months. The risk of CRC post-diverticulitis was higher in women (odds ratio [OR], 1.9), African Americans (OR, 2.0), and adults aged 18-65 (OR, 2.3).

“In a large cohort of more than 900,000 patients with a first episode of diverticulitis, we found that the incidence of cancer was 0.57%,” Dr. Cooper says. “Although this figure was at the lower end of those observed in previous studies, it was almost double the incidence of cancer in the general population. These differences persisted after adjusting for potentially confounding factors.”

Dr. Cooper notes that risk factors linked with CRC, for individuals with and without diverticulitis, are consistent with other epidemiologic studies. “The data suggest that lifestyle factors—such as avoidance of NSAIDs, smoking, alcohol, and obesity—may modify the risk,” he says (Table 1). The risk, he adds, seems to be consistent across subgroups, with the exception of seniors, which may be due to baseline prevalence being highest in this population (Table 2).

Cancer Location as It Pertains to Diverticulitis

“This is one of the largest population-based national studies that describes the epidemiology of acute diverticulitis and first-ever CRC after diverticulitis,” Dr. Cooper concludes. “Given the high burden of CRC, we advocate for colonoscopy within 6 months of the first occurrence of acute diverticulitis to screen for CRC, particularly if there are additional risk factors and no colonoscopy was performed within the last year.”

Dr. Cooper acknowledges some limitations in the study. “We were unable to collect data to compare the prevalence of CRC after complicated versus uncomplicated acute diverticulitis, as well as other ways of discerning the severity of diverticulitis, such as whether antibiotics were used, if the patient was hospitalized, duration of hospitalization, and whether drainage or surgery was performed,” he explains. For the same reason, the study team was unable to review the quality of prior colonoscopies, endoscopic abnormalities (eg, whether the CRC is in the same location in the colon as the diverticulitis), histology report, and CRC progression at the time of diagnosis. “I would like to see future research focus on the actual location of the cancer as it pertains to diverticulitis,” he says. “It would be of particular interest to see if the cancer and diverticulitis were located in the same segment of the colon.”