Polymyalgia rheumatica and giant cell arteritis induced by immune checkpoint inhibitors: A systematic literature review highlighting differences from the idiopathic forms

Introduction: An altered immune tolerance disturbed by immune checkpoint inhibitors (ICIs) may contribute to new-onset polymyalgia rheumatica (PMR) and giant cell arteritis (GCA). This systematic literature review (SLR) examines the characteristics of PMR and GCA-like syndromes following anticancer treatment with ICIs, summarizing their demographic, clinical and treatment-related features to provide insights whether they differ from the idiopathic forms. Methods: The SLR was conducted in Medline and EMBASE databases from inception to July 2024, and in the EULAR/ACR abstract database (2021-2023). ICI-induced PMR and GCA syndromes were compared to the primary forms of the diseases using data from studies that included both groups as comparators. For manuscripts lacking direct comparisons, we summarized the main findings and discussed the differences using systematic reviews or large observational studies on the primary forms. Results: From 1237 screened abstracts, 46 met the inclusion criteria, involving 358 patients (314 with ICI-PMR and 44 with ICI-GCA). ICI-PMR had an estimated pooled prevalence of 0.1% [95% CI: 0.07%, 0.14%] among ICI recipients and 15.9% [95% CI: 12.6%, 19.9%] among patients experiencing rheumatic immune-related adverse events. Patients with ICI-PMR had a male-to-female ratio of 1.7:1 and a mean age of 71 +/- 4 years. Most cases were associated with PD1/PDL1 blockers (87%). Clinical features included inflammatory pain in the girdles (100%), though pelvic girdle involvement was under-reported in some cases (3/28 studies). Peripheral arthritis was present in 35% of patients. Laboratory tests showed normal or slightly elevated inflammatory markers in 26% of cases. Glucocorticoids (GCs) led to symptom improvement in 84% of cases although 20% required immuno- suppressive treatment and 14% experienced relapses. ICI-GCA had a prevalence of 0.06% among ICI recipients, with equal gender distribution and a mean age of 71 +/- 5 years. Most patients received anti-PD1/PDL1 blockers (57%). Clinical manifestations included cephalic symptoms (75%), permanent visual loss (23%) and symptoms related to large-vessel involvement (54%). High- dose GCs were effective, with 96% achieving remission, though 17% experienced relapses. Conclusions: ICI-induced PMR and GCA may have distinct clinical profiles compared to idiopathic forms, with potentially milder symptoms and better treatment responses. Further studies are needed to confirm these findings and better understand the long-term outcomes and pathophysiology of these conditions.