What medical treatment is available for giant cell tumor of the tendon sheath?

Updated: Aug 06, 2019
  • Author: James R Verheyden, MD; Chief Editor: Harris Gellman, MD  more...
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In August 2019, pexidartinib was approved by the US Food and Drug Administration (FDA) for tenosynovial giant cell tumor (TGCT). It is the first systemic therapy for TGCT. Pexidartinib inhibits colony stimulating factor-1 receptor (CSF1R), a tyrosine kinase receptor. By binding to CSF1R expressed on monocytes, macrophages, and osteoclasts, pexidartinib prevents activation of interleukin-34. Blocking the production of inflammatory mediators by macrophages and monocytes is thought to inhibit tumor cell proliferation.

Approval of pexidartinib was based on the phase 3 ENLIVEN study, the first placebo-controlled study of a systemic therapy for TGCT. [39] The primary endpoint, overall response rate (ORR), showed significant improvement. At week 25, patients treated with pexidartinib (n = 61) had an ORR of 38%, compared with 0% for placebo-treated patients (n = 59). The complete response rate was 15% and the partial response rate was 23%. Of the 23 responders followed for a minimum of 6 months after the initial response, 22 maintained their response for 6 or more months. All 13 responders followed for a minimum of 12 months after the initial response maintained their response for 12 or more months.

Additionally, the ENLIVEN study documented statistically significant improvements in secondary end points (eg, mean changes in range of motion, physical function, and worst stiffness). [39] Liver toxicities were documented with pexidartinib that necessitated dosage reduction or discontinuance.

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