BRAF^V600E Metastatic Synovial Sarcoma Treated with BRAF & MEK Inhibitors Achieves Complete Response. A Case Report & Literature Review

—Synovial sarcoma is a rare soft tissue sarcoma. Treatment of synovial sarcoma includes surgery, radiation, pazopanib, and chemotherapy. Targeted therapies, such as B-Raf proto-oncogene, serine/threonine kinase (BRAF) inhibitors, are emerging as a potential treatment option. We describe the sixth case of a BRAF^V600E synovial sarcoma, the first extra-thoracic case. This case is the first to show a complete pathological response to BRAF & mitogen-activated protein kinase kinase (MEK) inhibitors.

—We treated a 22-year-old male with a left groin BRAF^V600E synovial sarcoma with doxorubicin, Ifosphamide & Sodium 2-Mercaptoethanesulfonate. When we identified BRAF^V600E in the tumor, the BRAF^V600E and MEK inhibitors (dabrafenib & trametinib) were initiated, followed by surgery, with a complete pathological response. Nine months after the surgery, a local recurrence prompted the resumption of dabrafenib & trametinib followed by radiotherapy, resulting in complete radiological response and the development of hemophagocytic lymphohistiocytosis treated with corticosteroids with resolution of symptoms.

—Panel sequencing of synovial sarcoma can identify targetable mutations. Treatment of BRAF^V600E synovial sarcoma with dabrafenib & trametinib can lead to complete pathological response and prolonged radiological response, as well as the rare adverse event of hemophagocytic lymphohistiocytosis. Prospective clinical trials are needed to evaluate the efficacy and safety of BRAF^V600E & MEK inhibitors as a therapeutic approach in BRAF^V600E synovial sarcoma.