Spectrum of EGFR gene mutations and ALK rearrangements in lung cancer patients in Turkey

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.

Testing for EGFR Mutations and ALK Rearrangements in Advanced Non-Small-Cell Lung Cancer: Considerations for Countries in Emerging Markets

The treatment of patients with advanced non-small-cell lung cancer (NSCLC) in recent years has been increasingly guided by biomarker testing. Testing has centered on driver genetic alterations involving the epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) rearrangements. The presence of these mutations is predictive of response to targeted therapies such as EGFR tyrosine kinase inhibitors (TKIs) and ALK TKIs. However, there are substantial challenges for the implementation of biomarker testing, particularly in emerging countries. Understanding the barriers to testing in NSCLC will be key to improving molecular testing rates worldwide and patient outcomes as a result. In this article, we review EGFR mutations and ALK rearrangements as predictive biomarkers for NSCLC, discuss a selection of appropriate tests and review the literature with respect to the global uptake of EGFR and ALK testing. To help improve testing rates and unify procedures, we review our experiences with biomarker testing in China, South Korea, Russia, Turkey, Brazil, Argentina and Mexico, and propose a set of recommendations that pathologists from emerging countries can apply to assist with the diagnosis of NSCLC.

Evaluation of epidermal growth factor receptor mutations and thyroid transcription factor-1 status in Turkish non-small cell lung carcinoma patients: A study of 600 cases from a single center

Background

This study aims to investigate the frequency, distribution, and morphological/immunohistochemical features of epidermal growth factor receptor mutations and to examine the possible relationship between the material type and technical success of mutation analysis in Turkish population with non-small cell lung cancer.

Methods

Between September 2012 and December 2015, a total of 499 consecutive, treatment-naïve patients (437 males, 163 females; mean age 61 years; range, 30 to 84 years) with primary or metastatic non-small cell lung cancer who underwent epidermal growth factor receptor mutation testing using Sanger sequencing method were retrospectively analyzed. Archival records and hematoxylin-eosine and immunohistochemically stained sections were re-examined. The thyroid transcription factor-1 and napsin A immunohistochemical stains were performed on tissue array blocks.

Results

Seventy-five mutations were detected in 70 patients (14%). The success rate of testing and intact deoxyribonucleic acid fragment length were significantly higher in the cytological material, compared to tissue specimens (p<0.001). The mutation rate in adenocarcinomas was 33.9% for women and 9.4% for men. The most common mutation was L746-E750del in exon 19 (29.3%), followed by the L858R mutation in exon 21 (28%). The mutation rate was the highest in micropapillary (40%) and lowest in solid (5.4%) adenocarcinomas. All epidermal growth factor receptor mutations, except for one, were positive for the thyroid transcription factor-1. The single nucleotide polymorphism Q787Q in exon 20 was observed in 79.6% of patients.

Conclusion

The frequency and distribution of epidermal growth factor receptor mutations in the Turkish patients with non-small cell lung cancer are similar to the European populations. These results also demonstrate that cytological materials are highly reliable for epidermal growth factor receptor mutation testing, and the probability of detection of wild-type epidermal growth factor receptor is low in cases of thyroid transcription factor-1 negativity.