Patients with Cancer and Immune Checkpoint Inhibitor-Induced Rheumatic irAEs Treated by DMARDs: The RHUMICI...

Immune checkpoint inhibitors (ICIs) can lead to immune-related adverse events (irAEs), including rheumatic manifestations affecting 5-10% of treated patients. Managing rheumatic irAEs is challenging, as the use of glucocorticoids (GCs) or disease-modifying antirheumatic drugs (DMARDs) raises concerns about potentially impairing ICI antitumour efficacy. The oncological safety of DMARDs used specifically for rheumatic irAE management remains poorly characterised. Our objective was to evaluate the oncological safety profile of various rheumatic irAE treatment strategies.

This single-centre retrospective observational study included 55 patients out of 104 who underwent rheumatological evaluation between July 2016 and October 2022. Patients were categorised into three groups: symptomatic treatment alone (analgesics/NSAIDs, n = 11), systemic glucocorticoids (GCs) only (n = 27), and conventional synthetic or biological disease-modifying antirheumatic drugs (csDMARDs and/or bDMARDs, n = 17). Overall survival (OS) and progression-free survival (PFS) were compared using a Kaplan-Meier analysis.

The three most frequent rheumatic irAE patterns were undifferentiated arthritis (n = 20), rheumatoid arthritis-like presentations (n = 14), and polymyalgia rheumatica (n = 11). Patients in the DMARD group had more severe irAEs (CTCAE grade ≥3: 30% vs. 15%, p < 0.01) and a higher baseline CRP (27.5 vs. 17.4 mg/L, p < 0.05), reflecting greater disease burden at treatment initiation. No significant difference was observed between groups for OS (p = 0.22) or PFS (p = 0.31) over a median follow-up of 34 months.

No detrimental oncological safety signal was identified across rheumatic irAE treatment strategies, including GCs combined with csDMARDs or bDMARDs. These results support the cautious use of DMARDs as GC-sparing agents when clinically indicated, consistent with current EULAR and ESMO guidelines, and underline the need for prospective trials to optimise immunosuppressive management in ICI-treated patients.