Clinical bottom line
Immune checkpoint inhibitor-induced colitis (ICI-colitis) is an increasingly recognized immune-related adverse event in patients receiving cancer immunotherapy. Recent evidence supports early recognition and a stepwise management approach, primarily with corticosteroids and selective immunosuppressants such as infliximab or vedolizumab for steroid-refractory cases. Emerging data suggest that gut-directed therapies may improve outcomes without compromising oncologic efficacy, but optimal timing, choice of immunosuppressant, and long-term safety remain areas of active investigation. Clinicians should maintain a high index of suspicion in patients on immune checkpoint inhibitors presenting with diarrhea or abdominal symptoms and tailor treatment based on severity and response.
What the evidence shows
Immune checkpoint inhibitors (ICIs), including anti–CTLA-4 and anti–PD-1/PD-L1 agents, have transformed cancer therapy but can trigger immune-related adverse events (irAEs), with colitis being among the most common and clinically significant gastrointestinal toxicities. The incidence of ICI-colitis varies by agent, higher with anti–CTLA-4 (up to 30%) than anti–PD-1/PD-L1 (5–10%) monotherapy, and even higher with combination regimens [1].
Current management guidelines, such as those from the American Society of Clinical Oncology (ASCO, 2021) and the National Comprehensive Cancer Network (NCCN, 2023), recommend grading colitis severity based on clinical symptoms and endoscopic findings. Mild cases (grade 1) may be managed conservatively, while moderate to severe colitis (grades 2–4) typically require systemic corticosteroids (prednisone 1–2 mg/kg/day or equivalent) [2,3].
For steroid-refractory or steroid-dependent colitis, selective immunosuppressants have become standard. Infliximab, a TNF-α inhibitor, has the strongest evidence base, showing rapid symptom resolution and steroid-sparing effects in multiple retrospective cohorts and prospective series [4]. Vedolizumab, a gut-selective α4β7 integrin antagonist, is emerging as an effective alternative with potentially less systemic immunosuppression, supported by observational studies reporting clinical remission in steroid-refractory cases [5].
Recent systematic reviews and meta-analyses (2020–2023) confirm that early initiation of immunosuppressants in steroid-refractory ICI-colitis improves clinical outcomes and may reduce hospitalization duration [6]. However, data on the impact of immunosuppression on cancer outcomes are mixed; some studies suggest no significant compromise in oncologic efficacy, while others raise concerns about potential attenuation of anti-tumor immunity, underscoring the need for individualized risk-benefit assessment [7].
Adjunctive therapies such as fecal microbiota transplantation (FMT) and novel biologics are under investigation but remain experimental. Endoscopic evaluation is increasingly recommended to confirm diagnosis, exclude infection, and guide therapy, as histologic severity may predict steroid responsiveness [8].
Caveats and uncertainty
Most evidence derives from retrospective cohorts, case series, and expert consensus guidelines rather than randomized controlled trials, limiting the strength of recommendations. The heterogeneity of patient populations, cancer types, ICI regimens, and colitis phenotypes complicates generalizability.
Optimal timing for escalation from corticosteroids to biologics is not standardized, and the comparative efficacy and safety of infliximab versus vedolizumab require prospective validation. Long-term safety data on immunosuppressive therapy in this context, including infection risk and impact on cancer progression or recurrence, remain limited.
Diagnostic challenges include differentiating ICI-colitis from infectious colitis or other causes of diarrhea, which may delay appropriate treatment. The role of biomarkers or predictive tools to stratify risk or guide therapy is an evolving area.
Finally, the balance between controlling colitis and preserving anti-cancer immunity is delicate; immunosuppression may theoretically reduce ICI efficacy, although current evidence is inconclusive and warrants further study.
How this may change practice
Clinicians managing patients on immune checkpoint inhibitors should maintain vigilance for gastrointestinal symptoms suggestive of colitis and adopt a multidisciplinary approach involving oncology and gastroenterology. Early endoscopic assessment can aid diagnosis and prognostication.
Prompt initiation of corticosteroids remains first-line for moderate to severe ICI-colitis, but clinicians should consider early escalation to infliximab or vedolizumab in steroid-refractory cases to improve outcomes and reduce steroid exposure. Vedolizumab may be preferred in patients at higher risk of systemic immunosuppression complications.
Awareness of emerging therapies and ongoing clinical trials may offer additional options in refractory cases. Close monitoring for infectious complications and cancer progression is essential during immunosuppressive treatment.
Ultimately, individualized treatment plans balancing colitis control and oncologic outcomes, guided by evolving evidence and multidisciplinary input, will optimize patient care.