PD-1 Blockade-induced Inflammatory Arthritis.
Radiology. 2018 Dec;289(3):616. doi: 10.1148/radiol.2018181532. Epub 2018 Oct 2.
Nobashi T1, Mittra E1.
A 75-year-old man presented for pembrolizumab treatment with a 2-month history of metastatic melanoma. A, Positron emission tomography (PET) prior to treatment revealed fluorine 18 fluorodeoxyglucose (FDG) uptake in the left lung (arrowheads) and in paraaortic 8L lymph node metastases (arrows). There was also uptake in the left knee related to prior surgery. Pembrolizumab (2 mg/kg) was administered every 3 weeks for 15 cycles. Ten months later, follow-up PET scan showed symmetric FDG uptake in multiple joints: shoulders, elbows, wrists, hips, and knees, and lymph nodes, with concomitant regression of the metastatic disease in the chest. At this time, the patient described intermittent joint and muscle pain which started 1 month after pembrolizumab administration and gradually worsened. Negative results from biopsy of a left inguinal lymph node, and the timing of these changes related to the initiation of pembrolizumab therapy and the widespread distribution of these changes in FDG uptake, led to the diagnosis of inflammatory arthritis with lymphadenopathy. B, Despite pembrolizumab discontinuation followed by 20 mg/day prednisone, these findings continued for 2 months (arrow = metastatic disease regression in the chest). His symptoms resolved after 5 months of prednisone. Pembrolizumab was subsequently resumed after 7 months due to recurrent melanoma. Pembrolizumab is an immune checkpoint inhibitor which targets PD-1 and is increasingly being used for multiple malignancies. Inflammatory arthritis is one of several immune-related adverse events that may occur during usage of immune checkpoint inhibitors (1). More than 70% of patients with PD-1 blockade monotherapy were reported to experience persistence of symptoms more than 3 months after cessation of therapy (2). Physicians should be aware of these immune-related adverse events when interpreting FDG PET scans in patients undergoing immune checkpoint inhibitor therapy.