pexidartinib and Synovitis--Pigmented-Villonodular

Tenosynovial giant cell tumor-diffuse type (diffuse TSGCT) is a benign but locally aggressive proliferative disorder of the synovium. Treatment is usually surgical, although in cases of extensive disease complete synovectomy is not possible and local recurrence rates are high. Pexidartinib (trade name Turalio®), a colony-stimulating factor-1 (CSF-1) inhibitor, was shown in a recent phase III trial to effectively treat diffuse TSGCT and is FDA approved for the treatment of adult patients with symptomatic diffuse TSGCT associated with severe morbidity or functional limitations and not amenable to improvement with surgery. Pexidartinib is available only through a restricted program under a risk evaluation and mitigation strategy (REMS) because of the risk of hepatotoxicity. Magnetic resonance imaging (MRI) is the preferred imaging modality for the diagnosis and surveillance of TSGCT. Here we present three patients with diffuse TSGCT of the knee who underwent multiple MRIs over several years while on pexidartinib. We describe the disease burden and signal characteristics on MRI and correlate with the response reported in the patients' medical records. Given that the use of pexidartinib and other CSF inhibitors is likely to increase, musculoskeletal radiologists should be aware of this novel non-operative treatment and the MRI appearance of diffuse TSGCT during therapy.

Topics: Adult; Aminopyridines; Colony-Stimulating Factors; Giant Cell Tumor of Tendon Sheath; Humans; Magnetic Resonance Imaging; Pyrroles; Synovitis, Pigmented Villonodular

Pexidartinib is the first approved medication in the USA for people with tenosynovial giant cell tumor (TGCT). The drug was approved based on the ENLIVEN study, which looked at pexidartinib (brand name, Turalio™), a medication taken by mouth (orally) for people with TGCT (also known as giant cell tumor of the tendon sheath [GCTTS] and pigmented villonodular synovitis [PVNS]) who are not able to have surgery because of the location and/or the size of the tumor. The study showed that pexidartinib is effective in treating people with TGCT because it shrunk the size of their tumors and improved their symptoms and their ability to function. In general, people treated with pexidartinib had side effects that were mostly mild that went away after treatment with pexidartinib was stopped. The most common side effects were hair color changes and tiredness (fatigue). Pexidartinib was also associated with liver problems (or hepatotoxicity), which started within the first 2 months of treatment. Due to the risk of liver problems, which may be severe and potentially life threatening, the researchers closely monitored participants' blood liver function tests before, during, and after participants in the study took pexidartinib.

Topics: Aminopyridines; Giant Cell Tumor of Tendon Sheath; Humans; Protein Kinase Inhibitors; Pyrroles; Synovitis, Pigmented Villonodular