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(P 41) PEXIDARTINIB UPFRONT IN A CASE OF TENOSYNOVIAL GIANT CELL TUMOR: PROOF OF CONCEPT FOR A TREATMENT PARADIGM SHIFT

    Author(s)

  • Emanuela Palmerini, MD, PhD

    Consultant Medical oncologist
    IRCCS Istituto Ortopedico Rizzoli
    Bologna, Emilia-Romagna, Italy

    • Co-Author(s)

  • GP

    Giuliano Peta, MD

    Radiology, IRCCS Istituto Ortopedico Rizzoli
    Bologna, Emilia-Romagna, Italy

  • GT

    Gianmarco Tuzzato, MD

    Orthopaedic and Traumatologic Clinic Prevalently Oncologic, IRCCS Istituto Ortopedico Rizzoli
    Bologna, Emilia-Romagna, Italy

Objective: Tenosynovial giant cell tumor (TGCT) is a rare, locally aggressive tumor of the joints, bursa, and tendon sheath that can cause considerable pain and substantial morbidity. Although surgery is the primary treatment for patients with TGCT, surgical resection is associated with high rates of recurrence, particularly for patients with diffuse TGCT. Pexidartinib, a colony-stimulating factor 1 receptor inhibitor, is approved by the US Food and Drug Administration for the treatment of adult patients with symptomatic TGCT associated with severe morbidity or functional limitations and not amenable to improvement with surgery.

Methods: A 32-year-old man presented with intra-articular diffuse TGCT with pain and received noncurative treatment for 5 years (2014-2019). In 2019, the patient was found to have extensive disease accompanied by pain and limited range of motion. The patient’s case was presented to a sarcoma Multidisciplinary Tumor Board, who determined that surgery would cause significant morbidity and macroscopic residual tumor.

Results: Due to the extent of disease, young age, and otherwise good health, treatment with pexidartinib was started through a compassionate use program at 800 mg/day. After dose reductions to pexidartinib at 400 mg/day and then 200 mg/day due to creatine phosphokinase elevations, the patient achieved a complete response after 2 years of treatment; pain was reduced and mobility was restored. The patient reported no side effects related to pexidartinib treatment. Treatment was stopped in 2022 for future family planning. After interrupting pexidartinib therapy, the patient’s wife had a successful pregnancy and delivery; however, the disease showed a slow but constant clinical deterioration, with a reduction in the range of movement of the affected knee and an apparent increase in widespread TGCT nodules.

Conclusion: Our case is unique because it provides support for pexidartinib use as upfront therapy for TGCT, instead of surgery, in selected cases.