Clinical Features of Rituximab-associated Gastrointestinal Toxicities

Background: Rituximab is effective in treating several cancers. Little is known about gastrointestinal adverse events associated with rituximab. We describe the clinical, endoscopic, and histologic features of rituximab-associated colitis (RC) at a tertiary care cancer center. Methods: We conducted a retrospective study of cancer patients who had received rituximab and had undergone a colonoscopy between 2000 and 2018. Patients with competing etiologies for colitis were excluded. Results: Of the 13,717 patients who had received rituximab during the study period, 1660 had undergone colonoscopy. Among them, 70 (4%) had RC. Median time from rituximab treatment to RC onset was 181 days. Fifty-three patients had clinical gastrointestinal symptoms: 39 had diarrhea, 19 had abdominal pain, 11 had blood per rectum, and 5 had a concurrent fever. The median duration of symptoms was 21 days. Fifty patients (71%) received treatment for RC: immunosuppressive therapy in 12, antimicrobial agents in 21, antimotility agents in 42, and supportive care in 42. Nine patients had mucosal ulceration on endoscopy, and 52 had features of active inflammation on histology. Thirty-nine patients needed hospital admission, and 2 needed intensive care unit admission. One patient had colonic perforation that required surgical intervention. Patients who had abnormal endoscopic findings needed more frequent hospitalization (P=0.024) and more treatment for RC (P=0.001). Conclusions: RC is usually a mild disease requiring supportive care only. Nonetheless, on rare occasions, it can be severe enough to lead to colonic perforation and intensive care unit admission. Steroids used with the chemotherapeutic regimen can hamper RC severity.