CTLA4 and rheumatoid arthritis: First, there was substantial heterogeneity across the included studies regarding cancer types (melanoma, NSCLC, urological cancers), pre-existing autoimmune diseases (psoriasis, rheumatoid arthritis, inflammatory bowel disease and others), and treatment regimens (anti-CTLA-4, anti-PD1/PDL1, monotherapy vs. combination therapy).