Pos0145 Whole-Body Mri Reveals a Distinct Imaging Phenotype in Patients With Arthralgia or Inflammatory Arthritis After Exposure to Immune Checkpoint Inhibitors

Background: Immune checkpoint inhibitors (ICIs) have revolutionised cancer treatment. However, immune related adverse events are common and a persistent inflammatory arthritis (IA) can develop. Furthermore, 43% develop arthralgia, which may reflect subclinical inflammation in a proportion [1]. The imaging phenotype and pathoanatomy of this syndrome is currently undefined. Objectives: We aimed to determine the imaging phenotype of ICI related arthralgia/IA to establish the pathoanatomical pattern of inflammation and subsequently inform optimum management. Methods: Patients with new arthralgia/IA during or ≤ 6 months after receiving an ICI (ICI + arthralgia/IA) underwent whole body MRI (WBMRI) with gadolinium contrast. Healthy controls (HC) with no joint symptoms were recruited. WBMRI joint, tendon, entheseal and axial inflammation was graded 0-2 by two independent blinded assessors and consensus reported; 0 = no pathology, 1 = indeterminate abnormality, 2 = definite abnormality (areas scored in Table 2). A total score of 0-34 was obtained for appendicular joint synovitis and erosions. Median total scores were compared between patients and controls (Mann-Whitney). The prevalence of grade 2 abnormalities was also compared (Chi squared). Results: Forty-five ICI + arthralgia/IA patients were included (Table 1). The predominant pattern of inflammation was an appendicular erosive synovitis with extracapsular features seen in polymyalgia rheumatica (PMR). Total appendicular joint synovitis scores were higher in arthralgia (9±6) and IA (12±9) than HC (2±2) (both p< 0.00001). Total erosions were also significantly higher in arthralgia (2±3) and IA (3±6) than HC (0±0.7) (both p< 0.00001). Prevalence of grade 2 abnormalities are described in Table 2. Glenohumeral (44%) and wrist (43%) joints were most frequently affected although 48% of the IA subgroup had grade 2 knee synovitis. Grade 2 finger flexor tenosynovitis (25%), ischial tuberosity enthesitis (22%) and trochanteric bursitis (47%) were also highly prevalent. Vertebral body (VB) anterior corner changes and sacroiliac (SI) bone oedema (BO) were uncommon. Endplate VB BO were attributed to degenerative changes/metastases with similar prevalence (33%) to HC (p=0.9). Conclusion: ICI + arthralgia/IA patients have a distinct pattern of erosive appendicular joint synovitis alongside extracapsular features typically seen in PMR. Subclinical inflammation in those with arthralgia alone is highly prevalent. Treatments used in predominantly appendicular IA/PMR may have greatest efficacy in these patients. REFERENCES: [1] Abdel-Wahab. Rheumatology 2019. Acknowledgements: NIL. Disclosure of Interests: Kate Harnden: None declared, Navkiran Sidhu: None declared, Emma Rowbotham: None declared, Sana Sharrack: None declared, Paul Emery Abbvie, Astra-Zeneca, BMS, Boehringer Ingelheim, Galapagos, Gilead, Janssen, MSD, Lilly, Novartis, Pfizer, Roche, Samsung, Abbvie, BMS, Lilly, Novartis, Pfizer, Roche, Samsung, Dennis McGonagle: None declared, Kulveer Mankia Abbvie, Galapagos, UCB, Serac Healthcare, Deepcure, Zura Bio, AstraZeneca, Gilead, Lilly, Serac Healthcare.