Inflammatory Arthritis Induced by Anti-Programmed Death-1 Shown in 68Ga-FAPI PET/CT in a Patient With Esophageal Carcinoma.

ABSTRACT A 30-year-old woman with esophageal squamous cell carcinoma experienced joint pain and swelling in bilateral knees, wrists, and hand joints during the course of neoadjuvant immunochemotherapy. She underwent 18F-FDG and 68Ga-FAPI PET/CT for response assessment of the tumor and evaluating her arthritis. 68Ga-FAPI PET/CT detected intense uptake in multiple joints, consistent with her polyarthritis. However, these joints showed only mild FDG uptake. The tumor was in complete response, and her polyarthritis was considered as inflammatory arthritis induced by anti-PD1.