Baseline characteristics of patients with ICI-IA and of ICI-treated controls without arthritis with available HLA DRB1 testing
| ICI-IA (NY, n=45) | ICI-IA (IL, n=20) | ICI-IA pooled (NY+IL, n=65) | ICI controls (IL, n=119) | P value (pooled vs controls) | |
| Age in years, mean (SD) | 69.8 (11.9) | 61.0 (11.6) | 67.1 (11.8) | 63.7 (13.5) | 0.1 |
| Female sex, n (%) | 9 (20) | 10 (50) | 19 (29) | 32 (27) | 0.7 |
| Cancer type, n (%) | p=0.004 | ||||
| Melanoma | 9 (20) | 10 (50) | 19 (29) | 59 (50) | |
| NSCLC | 8 (18) | 1 (5) | 9 (14) | 3 (3) | |
| Urothelial/RCC | 16 (36) | 1 (5) | 17 (26) | 25 (21) | |
| Other | 12 (26) | 8 (40) | 20 (31) | 32 (27) | |
| ICI regimen, n (%) | 0.4 | ||||
| PD-1/PD-L1 | 33 (73) | 13 (65) | 46 (71) | 74 (62) | |
| CTLA-4 | 0 (0) | 0 (0) | 0 (0) | 3 (3) | |
| Combination | 12 (27) | 7 (35) | 19 (29) | 41 (35) | |
| Current/past smoker, n (%) | 26 (58) | 11 (50) | 37 (60) | 69 (58) | 0.9 |
| CCP positivity, n (%) | 5 (11) | 2 (10) | 7 (11) | -- | -- |
| SE positivity, n (%) | 19 (42) | 9 (45) | 28 (43) | 55 (46) | 0.8 |
| Homozygous, n (%) | 5 (11) | 3 (15) | 8 (12) | 9 (8) | 0.4 |
.CCP, cyclic citrullinated peptide; ICI-IA, immune checkpoint inhibitor inflammatory arthritis; IL, Illinois; NSCLC, non-small cell lung cancer; NY, New York; RCC, renal cell carcinoma; SE, shared epitope.