CTLA4 and melanoma: For ordinal or nominal variables with more than two categories (PS, type of cancer, type of ICI, combined anti-neoplastic agent, best overall response), a reference category was established based on the most frequently observed irAE occurrence, except for combined anti-neoplastic agent (reference: none) and best overall response (reference: CR/PR) in each category (S1 Table): PS 0 (irAE occurrence: 43.5%), melanoma (irAE occurrence: 46.7%), anti-PD-1 and anti-CTLA4 antibodies (irAE occurrence: 44.4%).