Posted: Thursday, October 20, 2022
Salivary gland cancer is a rare cancer, consisting of 22 distinct subtypes. The subtypes vary widely in their genetic and clinicopathologic contents and are treated as distinctly. Gene fusions such as NTRK, however, tend to be a characteristic molecular feature of some salivary gland cancers. Carla M.L. van Herpen, MD, PhD, of Radboud University Medical Center, Nijmegen, the Netherlands, and colleagues attempted to identify genetic fusions or other actionable mutations that could be useful in genetically matching cancer therapies to salivary gland cancer subtypes. In fact, they found 1 patient (with secretory carcinoma) in 118 cases of salivary gland cancer subtypes to have an NTRK gene fusion. Published in Cancers, these data describe the occurrence of both known and novel gene fusions in this patient population and their potential role in selecting appropriate systemic therapies.
In the study, RNA and DNA were extracted from archival tumor tissue from 121 patients with salivary gland cancer subtypes. To detect relevant gene fusions in this cohort, a customized RNA-based next-generation sequencing panel was used. DNA was also sequenced using a targeted next-generation sequencing panel of 523 known cancer-related genes.
A fusion transcript was detected in about half of all patients. When the investigators looked to the tumor subtype, a fusion transcript was found in 75.0% of patients with adenoid cystic carcinoma, 28.6% of patients with salivary duct carcinoma, 40.0% of patients with mucoepidermoid carcinoma, and 37.5% of patients with acidic cell carcinoma. In the 75% of patients with adenoid cystic carcinoma in which a detection occurred, the same gene fusion, MYB/MYBL1-NFIB, was found in all patients (n = 33)—but not in patients with any other cancer subtype tested.
Only 1 patient of 118 cases (who had secretory carcinoma) was found to have an NTRK gene fusion. Furthermore, pan-TRK immunohistochemistry (IHC) false positivity was noted in 73.8% of cases 79 of 107). “Given the overall low prevalence of NTRK gene fusions, sensitivity of IHC to detect NTRK gene fusions could not be assessed reliably,” the authors noted.
Disclosure: For full disclosures of study authors, visit mdpi.com.