Characterization of arthralgia induced by PD-1 antibody treatment in patients with metastasized cutaneous malignancies

Background PD-1 antibodies (PD1ab) are increasingly used in metastatic melanoma and other malignancies. Arthralgia is an underestimated side effect of PD-1 antibody treatment with unknown cause. Our aim was to characterize PD1ab-induced arthralgia. Patients and methods We retrospectively included patients with metastatic cutaneous malignancies treated with pembrolizumab or nivolumab +/- ipilimumab at the National Center for Tumor Diseases (Heidelberg) between 01/2013 and 09/2016. Arthralgia was characterized by laboratory diagnostics, imaging, and if indicated, rheumatologic consultation. Results 26 of 195 patients (13.3%) developed arthralgia. The median onset of symptoms was 100 days (7-780 days). Most frequently, arthralgia involved large joints (shoulders, knees) in a predominantly symmetrical pattern. Only two patients were seropositive for rheumatoid factor and/or anti-citrullinated protein antibodies. Ten patients developed the clinical picture of arthritis, with seven of them showing synovitis in MRI or PET/CT. Five patients showed inflammation in joints pre-damaged by osteoarthritis. In 11 patients arthralgia could not be specified. The majority of patients was satisfactorily treated with non-steroidal anti-inflammatory drugs (NSAIDs), 23.1% required additional low-dose corticosteroids and only 7.6% of our patients received further immunosuppressive treatment. Patients with arthralgia showed a better treatment response and improved PFS and OS. Conclusion Arthralgia is frequent during PD1ab treatment. The clinical picture varies between synovitis of predominantly large joints, progressive osteoarthritis and arthralgia without evident joint damage. Vast majority of cases can be satisfactorily managed by NSAID and/or low-dose corticosteroids.