NTRK-fusion detection in thyroid and salivary gland cancer offers a targeted therapy with NTRK-inhibitor

Abstract

NTRK-fusion in cancer is rare but it offers targeted therapy with NTRK-inhibitor. NTRK fusion is not a point mutation. NTRK fusion is an oncogenic driver, NTRK mutation is not an oncogenic driver. Patients with NTRK point mutation do not respond to NTRK-targeted therapy. NTRK fusion was detected in secretory carcinoma. Secretory carcinoma was a new entity, first described in 2010, classified by NTRK-fusion. It is often misdiagnosed, and standard pathology often fails to distinguish it from another histology subtype of salivary gland carcinoma, so its frequency can be higher than has been reported. Therefore, different examinations are needed in order to obtain a correct diagnosis. In thyroid gland carcinoma, NTRK fusion-positive carcinomas are associated with clinically aggressive disease with a high metastatic rate. Therefore NTRK-fusion test should be performed in thyroid cancer patients with recurrence and unresectable disease, metastatic thyroid cancer, Radioactive Iodine (RAI)-refractory disease, and invasive disease. Immunohistochemistry with antibody against TRKA, TRKB, and TRKC can be used to identify TRK protein expression in salivary gland cancer so this test can be used for screening in all salivary gland cancers. NGS or FISH are tools that can be used to confirm NTRK fusion. Detection of NTRK fusion allows new hope for cancer patients with refractory therapy.