Aim:
To evaluate the incidence and economic burden of autoimmune colitis secondary to checkpoint inhibitors, requiring treatment with infliximab, in a major tertiary referral hospital.
Methods:
A retrospective observational cohort study was conducted. Patients were identified using pharmacy dispensing records, Drug and Therapeutics Committee individual patient use applications and International Classification of Diseases, 10th Revision codes. All patients admitted between May 2015 and May 2017, who received at least one dose of infliximab for treatment of autoimmune colitis confirmed via sigmoidoscopy or colonoscopy with biopsy were eligible for inclusion.
Results:
Fourteen patients were admitted to hospital with autoimmune colitis secondary to checkpoint inhibitors requiring infliximab over a two-year period. Of these, 13 patients had metastatic melanoma. A total of 18 doses of infliximab were administered at a cost of $34,441. Eighteen admissions were required, resulting in a cumulative total of 98 bed days (average length of stay: 5.4 days ± 4.0) at a cost of $169,344 to the hospital.
Twelve patients received combination treatment with ipilimumab and nivolumab and two patients pembrolizumab prior to developing autoimmune colitis. All cases of colitis were classified as steroid resistant following treatment with methylprednisolone or hydrocortisone (mean treatment duration 1.6 days ± 1.5) at a cost of $310.
Conclusion:
Autoimmune colitis, secondary to checkpoint inhibitors, requiring treatment with infliximab resulted in treatment costs of approximately $200,000 at a major tertiary hospital over a 2 year period. When approving applications for the addition of checkpoint inhibitors to hospital formularies and clinical trial protocols, Drug and Therapeutics Committees need to take into account the estimated economic expenditure for treatment of common autoimmune adverse drug reactions as the use of these therapies continues to expand.