Fibroblast growth factor receptor 1 amplification in laryngeal squamous cell carcinoma

Abstract

Fibroblast growth factor receptor 1 (FGFR1) has been noted to be amplified in a variety of squamous cell carcinomas (SCCa) of the head, neck, and lung and increased copy number (CN) is a predictor of poor outcomes. FGFR1 is a therapeutic target for lung SCCa and inhibition therapy is currently in clinical trials. Absolute quantification of FGFR1 from formalin fixed paraffin embedded (FFPE) tissue of laryngeal SCCa was examined in this retrospective study. A droplet digital polymerase chain reaction (ddPCR) was used for absolute quantitation of the FGFR1 gene CN. Of the 74 samples analyzed, FGFR1 CN analysis revealed 54% of samples had CN greater than 2 copies/cell (1.8–2.2 copies/cell), and 38% had CN values greater than 3. The mean and standard deviation FGFR1 CN was 4.17 ± 1.46 CN for African American patients (n = 41) and 3.78 ±1.85 CN for Caucasian patients (n = 31). Further, 60.9% of specimens from African Americans demonstrated increased FGFR1 CN compared to 48.4% of Caucasians. Two SCCA samples from Native American demonstrated increased FGFR1 CN (4.19 and 3.01 CN). The level of FGFR1 amplification did not correlate with tumor stage, lymph node staging, or metastasis. In this population, the proportion of patient samples with an FGFR1 amplification was three times higher than in reported for SCCA of the head and neck. Further, increased FGFR1 CN was observed in two racial groups not previously reported: African Americans and Native Americans. However, FGFR1 amplification is not prognostic in laryngeal squamous cell carcinomas.