Performance of standard procedures in detection of EGFR mutations in daily practice in advanced NSCLC patients selected according to the ESMO guideline: a large Caucasian cohort study

Hantson et al. Translational Respiratory Medicine 2014, 2:9 http://www.transrespmed.com/content/2/1/9 RESEARCH Open Access Performance of standard procedures in detection of EGFR mutations in daily practice in advanced NSCLC patients selected according to the ESMO guideline: a large Caucasian cohort study Inge Hantson1, Christophe Dooms1,2, Eric Verbeken3, Peter Vandenberghe4, Liesbet Vliegen4, Tania Roskams3, Sara Vander Borght3, Kris Nackaerts1,2, Isabelle Wauters1 and Johan Vansteenkiste1,2* Abstract Background: ESMO consensus recommends EGFR mutation testing in never/former light smokers (<15 pack-years) or patients with non-squamous NSCLC. The aim of this work was to determine the frequency and clinical predictors of EGFR mutations, and the role of specimen sampling tests, in Caucasian standard practice setting. Methods: We screened 297 patients according to this consensus. Mutational analysis of EGFR was performed using the Therascreen EGFR RGQ PCR mutation kit. Clinical and pathological correlative data were collected. Results: An EGFR activating mutation was found in 32 patients (11%), twelve exon 19 deletions, two exon 18 and eighteen exon 21 point mutations. Most were in females, but half were in smokers. Negative TTF-1 staining had a very strong negative predictive value (all except one patient had TTF-1 positive adenocarcinoma). Both biopsies as well as cytology specimens (mainly EBUS-TBNA) did well: 24 mutations in 213 biopsy samples (11.2%) and 8 in 84 cytology samples (9.5%), respectively. The Therascreen acted as a sensitive test in all types of samples: 7 activating mutations were found in samples rated to have <5% of tumour cells, and there were only 4 test failures in the whole series. Conclusion: In this Caucasian standard practice NSCLC cohort, tested according to the ESMO consensus, activating EGFR mutation occurred in 11% of the patients. Half of these were in former/current smokers. With our sampling technique and use of the Therascreen kit, EBUS-TBNA cell blocks performed as good as biopsies. Keywords: Predictive factors; Real-time quantitative polymerase chain reaction (rt-qPCR); EGFR mutation; Endobronchial ultrasound; Biopsy methods Background About 85% of all lung cancer patients have non-small cell lung cancer (NSCLC), and the majority presents with advanced stage disease at the time of diagnosis. The standard of care for these patients is platinum-based doublet chemotherapy [1]. This ‘any platinum doublet fits all’ strategy results in a median overall survival of 8 to 10 months and a 1 year survival rate of about 33%. * Correspondence: 1 Respiratory Oncology Unit, Department Pulmonology, University Hospitals KU Leuven, Leuven, Belgium 2 Department of Clinical and Experimental Medicine, Lab for Pulmonology, University of Leuven, Leuven, Belgium Full list of author information is available at the end of the article Different strategies to prolong survival have been developed. Besides customisation of chemotherapy according to histological subtype [2], and the use of maintenance therapy in order to achieve prolonged tumour control [3], the most important change during the last decade was the introduction of treatment guided by the tumour’s genetic profile. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) heralded this evolution, when very pronounced and durable responses to these agents were noted early in this century [4]. A few years later, somatic mutations in the EGFR gene were discovered in these highly responsive tumours. They affect the tyrosine © 2014 Hantson et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. Hantson et al. Translational Respiratory Medicine 2014, 2:9 http://www.transrespmed.com/content/2/1/9 kinase domain of the EGFR – involving exons 18 until 21 – and lead to constitutive activation of the receptor, independent of ligand binding. The tumour becomes highly dependent on this pathway, and thus very sensitive to blockade of this pathway by TKIs [5]. Recent randomised trials demonstrated that the presence of an EGFR activating mutation was the best predictive factor for response and progression-free survival (PFS) to EGFR TKIs when compared to platinum doublet chemotherapy in the first-line therapy of advanced NSCLC [6,7]. Given this strong benefit of EGFR-TKIs in patients with a tumour with an EGFR activating mutation (EGFR mut + tumour), molecular profiling became necessary in the assessment of stage IV NSCLC. EGFR mutations are known to be associated with clinical characteristics such as never-smoking status, female gender, adenocarcinoma histology and South-East Asian ethnicity [8]. Adenocarcinoma is by far the most common NSCLC histology in South-East Asia, and about 40% of these tumours are EGFR mutant [9]. The EGFR mutation occurrence is much lower in Caucasian populations. As both gefitinib and erlotinib are now registered in Europe for the treatment of patients with an EGFR mut + tumour, selection criteria to identify which patients are most likely to have an EGFR mutation are needed. Based on the South-Asian experience and the occurrence of the different NSCLC histologies in Europe, a European guideline (ESMO consensus [1]) recommends EGFR mutation testing in never-/former light (<15 pack-years) smokers or patients with non-squamous NSCLC. As a consequence and in contrast with 10 years ago, precise histological subtyping and EGFR testing is now mandatory. Many colleagues of the multidisciplinary team involved in the diagnostic flow of NSCLC – pulmonologists, surgeons and radiologists – need to optimise biopsy samples (size, content of tumour cells). Until now, the most common diagnostic procedure for the diagnosis of NSCLC was bronchoscopy, which may however not always provide enough tissue for molecular analysis. We therefore evaluated the performance of different small tissue samples obtained during bronchoscopic procedures, such as bronchial biopsies and endobronchial ultrasound guided transbronchial needle aspirations (EBUS-TBNA), in the molecular diagnostic setting of NSCLC. Study aims were (1) the frequency of EGFR mutations (exon 18–21) in a large Caucasian cohort; (2) clinical and pathological predictors; (3) the sensitivity of the Therascreen kit; and (4) the performance of cytology versus biopsy samples for mutation analyses. Methods Study subjects All consecutive EGFR mutation analysis reports in the period from September 2010 until December 2011 Page 2 of 8 included were retrieved from the molecular genetics database. During this period, our local policy was to order EGFR mutation testing in all patients diagnosed with advanced NSCLC, either of adenocarcinomas or not-otherwise specified (NOS) histology, irr (...truncated)