Simple SummaryRadiation-induced colitis and proctopathy (RICAP) is a recognized adverse effect of radiation therapy (RT) that can adversely affect cancer patients’ quality of life. However, data on the clinical characteristics and outcomes of RICAP are scarce. Our study found that acute RICAP (ARICAP) has non-bloody diarrhea as the predominant symptom, whereas chronic RICAP (CRICAP) has mostly bloody diarrhea. ARICAP patients more often received medical management, whereas CRICAP patients with bleeding more often received argon plasma coagulation (APC). APC treatment may be useful in patients with endoscopically apparent bleeding, but it did not significantly reduce the bleeding recurrence or RICAP symptoms. More research is needed to better characterize and distinguish between the two entities.AbstractBackground: RICAP is a recognized adverse effect of radiation therapy (RT) that can adversely affect cancer patients’ quality of life. Data on the clinical characteristics and outcomes of RICAP are scarce. We aimed to analyze the clinical and endoscopic characteristics of acute or chronic radiation-induced colitis and proctopathy (ARICAP and CRICAP) based on symptom onset after RT (≤ or >45 days, respectively). Methods: This is a retrospective observational study of a single tertiary cancer center, from January 2010 and December 2018, of cancer patients with endoscopically confirmed ARICAP and CRICAP. We conducted univariate and multivariate logistic regression analyses to associate clinical variables with endoscopic and medical outcomes. Results: One hundred and twelve patients were included (84% Caucasian; 55% female; median age of 59 years); 46% had ARICAP with non-bloody diarrhea as the predominant symptom, whereas 55% had CRICAP with mostly bloody diarrhea. Neovascularization was the most frequent finding on endoscopy, followed by bleeding. ARICAP patients more often received medical management (p< 0.001), whereas CRICAP patients with bleeding more often received argon plasma coagulation (APC) (p= 0.002). Female sex and undergoing less-intense RT treatments were more associated with medical treatment; bleeding clinically and during the endoscopy was more associated with APC treatment. However, APC treatment did not significantly reduce bleeding recurrence or RICAP symptoms. Conclusion: Patients with ARICAP and CRICAP experience different symptoms. Medical management should be considered before endoscopic therapy. APC may be useful in patients with endoscopically apparent bleeding.