Investigation of EGFR and ALK mutation frequency and treatment results in advanced non-small cell lung cancer.

Aim: Lung cancer has opened a new era in cancer treatment by elucidating the tumor's molecular structure and identifying the targetable mutations. Identifying the targeted mutations in lung cancer constitutes one of the main steps of treatment planning. The frequency of EGFR (epidermal growth factor receptor gene) and ALK (anaplastic lymphoma kinase gene) mutations in non-small cell lung cancer (NSCLC) also varies in populations depending on ethnicity, gender, smoking, and histopathological subtype. In general, limited data are available regarding the frequency and regional distribution of these mutations in the Turkish population. Our study aimed to determine the frequency of EGFR and ALK mutations in patients with advanced-stage NSCLC and compare the clinical characteristics, treatment, and survival results of cases with mutations with the group without mutations.

Materials and methods: In our study, 593 patients with advanced-stage NSCLC diagnosis and mutational analyses were evaluated retrospectively. Demographic characteristics, tumor stages (tumor, node, metastasis, TNM), EGFR and ALK analysis results, treatments applied, and survival of the cases were recorded. EGFR analysis, exon 18, 19, 20, and 21 mutations were studied with real-time PCR (RT-PCR) Rotor-Gene system from patients' samples. For ALK analysis, the ALK Break Apart kit (Zytovision GmbH; Germany) was used with the fluorescent in situ hybridization (FISH) method.

Results: In our study, EGFR mutation was detected in 63 patients (10.6%) and ALK mutation in 19 patients (3.2%) out of 593 patients. EGFR mutation was observed more frequently in women and non-smokers (P = 0.001, P = 0.003). No correlation was found between the presence of EGFR mutation and metastases regions and recurrence (P > 0.05). ALK mutation was observed more frequently in non-smokers and females (P = 0.001, P = 0.003). Patients with ALK mutations were younger than other groups (P = 0.003). There was also no significant relationship between ALK mutation and metastates regions and recurrence after treatment (P > 0.05). Patients with EGFR or ALK mutations had a longer life span than other cases (P = 0.474). Those who had ALK mutations and received targeted therapy had a longer average life expectancy (P < 0.05). No difference was observed in those who had EGFR mutations and received targeted treatment in terms of survival (P > 0.05).

Conclusion: In our study, conducted in the Aegean region of Turkey, the positivity rates of EGFR and ALK mutations were found to be at similar rates with the Caucasian race across the world. EGFR mutation was more common in women, non-smokers, and patients with adenocarcinoma histology. ALK mutation was also detected more frequently in younger patients, women, and non-smokers. Patients with EGFR and ALK mutations had a longer life expectancy than those without the mutation. It was observed that testing patients diagnosed with advanced-stage NSCLC for genetic mutations of the tumor in the first step of the treatment and initiating treatment in patients with mutations provided a significant survival advantage.