Ab1388 Clinical Patterns and Longterm Outcomes of Arthritis Induced by Immune Checkpoint Inhibitors. A Multicenter Study

Background: Immune-related adverse events (irAEs), including inflammatory arthritis (IA), have become a subject of increasing interest within the rheumatology community. Unraveling the prognosis and treatment needs for individuals experiencing ICI-induced arthritis remains a complex task, as outcomes can vary widely among patients. Objectives: To analyse the clinical presentation, treatment response, and outcomes of IA induced by immune checkpoint inhibitors (ICIs) in patients with cancer. Methods: Retrospective observational study conducted from January 2015 to December 2023 at four tertiary university hospitals. Results: We included 119 patients (63% male) with a mean age at diagnosis of 66 ± 11 years. The primary underlying cancers were lung (41%), melanoma (18.5%), renal-urothelial (12.6%), hematologic (6%), and other neoplasms (6%). ICIs comprised monotherapy (91%) and combined regimens (9%). In the monotherapy group, most patients received PD-1/PD-L1 inhibitors, with only one case receiving a CTLA-4 inhibitor. Thirteen patients (11%) underwent additional oncologic treatments. Nine patients (7.5%) developed other rheumatic irAEs, including sicca syndrome (9 cases), myositis (1 case), and sarcoidosis (1 case), while 41 (34.4%) experienced one or more non-rheumatic irAEs, usually before or simultaneously with rheumatic syndromes. Of the 119 patients, 83 (70%) developed peripheral arthritis, and 36 (30%) exhibited a polymyalgia rheumatica (PMR)-like syndrome. Among patients with peripheral arthritis, the median time from cancer diagnosis to ICI initiation was 6 months (IQR 25th–75th percentile: 1.8–14.0 months), and from ICI initiation to joint involvement was 127 days (IQR 51–242 days). Patients receiving combined therapy tended to develop symptoms earlier than those on monotherapy. IA manifestations included polyarthritis (53 cases), oligoarthritis (24 cases), and monoarthritis (6 cases). The final diagnoses were undifferentiated arthritis in 53 (44.5%) patients, rheumatoid arthritis (RA)-like in 19 (16%), psoriatic arthritis-like in 8 (7%) and reactive arthritis-like in 3 (2.5%). Immunological markers showed positive ANA in 23.7% (14/59) and positive RF and ACPA in 3.3% (3/59). IA treatments included the use of NSAIDs in 58% (48/83) of cases, GCs in 96% (80/83), HCQ in 44.5% (37/83), MTX in 12% (10/83), SSZ in 1.2% (1/83) and anti-TNF in 1.2% (1/83). The median follow-up time for patients with arthritis was 9 months (IQR 3.4–16). At the last visit, ICIs had been discontinued in 55.4% (46/83) of patients. Thirty-six percent (30/83) achieved sustained drug-free remission (SDFR), while the rest (64%, 53/83) continued treatment. Among the 36 patients with PMR-like syndrome, the median time from cancer diagnosis to ICI initiation was 2 months (IQR 0.5–5.5 months), and from ICI initiation to PMR onset was 118 days (IQR 59–219 days). Besides GCs, 17% (6/36) were on steroid-sparing agents (MTX, leflunomide, or HCQ). The median follow-up was 12.4 months (IQR 5.2–21). ICIs were discontinued in 33.3% (12/36) of these patients, with 35% (11/36) achieving SDFR, while 69.5% (25/36) remained on treatment. Conclusion: The most frequent patterns of IA induced by ICIs are undifferentiated arthritis (44.5%), PMR-like syndrome (30%), and RA-like (16%). Forty-five percent of patients required a csDMARD/bDMARD. At the last follow-up, 65% of cases remained with active arthritis, either persistent or presenting intermittent flares. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: José A Gómez-Puerta Astra-Zeneca, GSK, Galápagos, Lilly, Pfizer, Otsuka, Sanofi, Arturo Llobell: None declared, Andrés Ponce: None declared, Antonio Gómez-Centeno Abbvie, Galápagos, Lilly, Pfizer, Ana Milena Millán Arciniegas: None declared, Héctor Corominas Abbvie, Amgen, Galápagos, Lilly, Pfizer, Sanofi, Joan Miquel Nolla: None declared, Javier Narváez Boehringer Ingelheim, GSK, Pfizer.