The Presence of HER2 Exon 20 Insertion in Patients with Central Nervous System Metastases from Non-Small Lung Cancer—A Potential Application in Classification for Therapy

Introduction: HER2 (ErbB2/neu) is a member of the ErbB family of four structurally related receptors of tyrosine kinase activity. Overexpression of ErbB-1 (EGFR) and HER2 is found in many human cancers, but the presence of these genes mutations determines the effectiveness of EGFR and HER2 tyrosine kinase inhibitors in the therapy of non-small cell lung cancer (NSCLC). Material and Methods: To search for insertions of the HER2 gene in exon 20 in 150 brain metastases of non-small cell lung cancer patients, we used a PCR technique based on analysis of amplified DNA fragment lengths. We also compared the HER2 mutational status with clinicopathologic features and the presence of EGFR and BRAF mutations. Results: HER2 mutation was present in one male, non-smoking patient with low differentiated adenocarcinoma (0.67% of all patients and 1.5% of patients with adenocarcinoma). The mutations of EGFR and BRAF genes were not found in HER2-mutated patient. Conclusions: The literature data suggests that patients with HER2 mutations may be sensitive to tyrosine kinase inhibitors of both EGFR and HER2 receptors (e.g., afatinib). Therefore, the identification of new driver mutations in NSCLC can improve the quality of patient care by enabling the use of correct molecularly targeted therapies.