Safety of sequential immune checkpoint inhibitors after prior immune therapy

Background The use of immune checkpoint inhibitors (ICI) has transformed cancer treatment. Subsequent ICI use has become increasingly common following disease progression. We aim to evaluate the safety and tolerability of the sequential ICI treatment modality. Methods Retrospective review of confirmed carcinoma from January 2014 to December 2018. Patients were categorized into "initial ICI arm" and "sequential ICI arm" defined as patients receiving single, dual or chemo-immunotherapy ICI following an initial ICI regimen. Primary outcome was the development of a new or recurrent immune related adverse event (irAE) during sequential therapy. Secondary outcomes were the number of cycles prior to the development of irAE and grade of irAE. Results A total of 483 patients received ICI during the timeframe. Of those, 22 patients received sequential ICI. The diagnoses included ten lung cancer, seven melanoma, four renal cell carcinoma and one bladder cancer. 16 patients received single agent ICI following the initial ICI, three patients received dual ICI following the initial ICI, one patient received chemotherapy-immunotherapy following initial ICI, and two patients received chemo-immunotherapy after dual ICI. Four patients developed new irAE and one patient developed the same irAE on sequential treatment. A higher proportion of patients experienced grade 3 irAE in the sequential arm compared to the initial ICI arm (p = 0.03). No statistical difference was found between the development of irAE and the number of cycles prior to development of irAE in either treatment groups (p = 0.5). Conclusion Our data shows overall safety of sequencing ICI when close monitoring was employed.