Increased risk of colon cancer after acute appendicitis: a nationwide, population-based study.

Background: Acute appendicitis is the most common digestive disease requiring emergency surgery. Colorectal cancer is the third most common cancer in France. An increased risk of colorectal cancer after acute appendicitis has been suggested. We aimed to assess the frequency of hospitalization for colon cancer after appendicitis in a nationwide analysis. Methods: Using the French Hospital Discharge Database (PMSI), we included all patients aged 18-59 years presenting with acute appendicitis between 2010 and 2015. Univariate and multivariate analyses were performed to compare colon cancer occurrence in these patients vs a control-matched population with a hospital stay for trauma in the same period. Patients presenting strong risk factors for colorectal cancer were excluded. Findings: A total of 230,349 patients with acute appendicitis (exposed group) were included. We used a propensity score to match each exposed patient with two unexposed patients (controls) to ensure the comparability of the groups, resulting in a control group of 460,698 patients. Univariate analysis found significantly more colon cancer in the appendicitis group, especially during the first year after appendicitis (5 per 10,000 vs 1 per 10,000, p < 0.000, this corresponds to 111 patients in the appendicitis group), namely within the first 6 months. Survival analysis confirmed patients treated for appendicitis present a 4 times higher risk of being diagnosed with colon cancer than control patients during the first year of follow-up (sHR = 4.67 (95% CI: 3.51-6.21), and 8 times higher during the first 6 months (sHR = 8.39; 95% CI: 5.41-12.99). The association was even more marked for right-sided colon cancer (sHR = 8.25; 95% CI: 5.03-13.54 during the 1st year). While the risk of diagnosis of colon cancer was also significant for patients over 40 years, it was even greater in patients under 40 years, who had between a 6-fold and 12-fold increase in risk. Interpretation: In this population-based study, we found that acute appendicitis seems to be a warning sign for colon cancer (reverse causality) in both middle-aged and younger adults. The risk of presenting with cancer colon was higher during the first six months after acute appendicitis. This raises the issue of routine diagnostic work-up in adults presenting with acute appendicitis. Funding: Regional Council of Burgundy.