Despite the growing indications of immune checkpoint inhibitors to treat advanced stage cancers, true inflammatory arthritis is an infrequently reported immune-related adverse event. Arthralgia is commonly reported in clinical trials with prevalence ranging from 1-43%1, with no clear breakdown of grade or management paradigm.
We report a case of evolving large joint polyarticular inflammatory arthritis, limiting mobility, in a 55 year old male patient receiving pembrolizumab for metastatic melanoma after 10 months on therapy. At the onset of arthritis, PET/CT demonstrated complete tumour response and is durable 8 months later. This patient obtained good symptomatic control with cessation of pembrolizumab, three months of weaning prednisolone and opioid analgesia. Inflammatory arthritis was demonstrated by imaging, synovial fluid aspirate and synovial biopsy.
A review of the limited number of case reports, most with combination anti-PD1 and anti CTLA-4 agents, have management that vary from intra-articular glucocorticoids to systemic glucocorticoids, escalating to steroid sparing agents and anti-tumour necrosis factor medications. There appears to be a dichotomy between treating teams who administered glucocorticoid therapy and those who avoided use. Additionally, the majority of patients who developed inflammatory arthritis had either partial or complete tumour response, with unclear prognostic significance2-6. Future research is required to formulate a validated treatment algorithm to aid oncologists in management of this often disabling rheumatological adverse event.