The suitability of small biopsy and cytology specimens for EGFR and other mutation testing in non-small cell lung cancer

Background: Patients with advanced non-small cell lung cancer (NSCLC) benefit from treatment with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) when their tumor harbors an activating EGFR mutation. As the majority of NSCLC patients present with advanced disease, cytology and small biopsy specimens are frequently the only tissue available for mutation testing, but can pose challenges due to low tumor content. We aim to better define the suitability of these specimens for mutation testing. Methods: NSCLC cases referred to our institution for mutation testing over a 15-month period were retrospectively reviewed. Specimens were tested for mutations including EGFR, KRAS, and BRAF, using a multiplex PCR assay (OncoCarta Panel v1.0) and analyzed on the Agena Bioscience MassARRAY platform. Results: A total of 146 specimens were tested, comprising 53 (36.3%) resection specimens (including 28 lung resection specimens), 55 (37.7%) small biopsy specimens and 38 (26%) cytology specimens. Of 142 cases with sufficient DNA for mutation testing, EGFR mutations were detected in 31 specimens (21.8%), KRAS mutations in 31 specimens (21.8%) and BRAF mutations in three specimens (2.1%). There was no significant difference in the EGFR mutation rate between lung resection (10 of 28 cases; 35.7%), small biopsy (9 of 53 cases; 17%), and cytology specimens (8 of 36 cases; 22.2%). Conclusions: Our results support the utility of small biopsy and cytology specimens for mutation testing. Careful evaluation of the adequacy of small specimens is required to minimize the risk of false negative or positive results

EGFR–co-mutated advanced NSCLC and response to EGFR tyrosine kinase inhibitors

Objectives The evolution of EGFR tyrosine kinase inhibitors (TKIs) has changed the landscape of disease for a subset of patients with NSCLC. Most patients with an EGFR mutation respond to these drugs; however, a proportion show limited or no tumor response. We explored the impact of co-mutation (double or multiple mutation), compared with a single mutation, of the EGFR gene on response to TKIs in a series of patients with metastatic NSCLC. Methods We retrospectively analyzed the mutation profiles of nonsquamous NSCLC tested at Royal Prince Alfred Hospital between 2012 and 2015 by MassArray using the OncoCarta v1.0 panel. Patients with metastatic disease whose tumors had sensitizing EGFR mutation(s) were included. The primary end point was progression-free survival (PFS). We used the Kaplan-Meier method for PFS and overall survival; the log rank test was used to compare groups with and without co-mutation. Multivariable analysis was done for PFS; response rate was assessed using chi-square and logistic regression analysis. Results A total of 62 patients were included, and of these, eight (12.9%) had a co-mutation. The median PFS and overall survival times were 11.5 and 26.3 months, respectively. Patients with EGFR co-mutation had a significantly shorter median PFS than those with a single mutation (5.7 months versus 12.3 months, p = 0.02). The response rate to TKIs was significantly worse in those with co-mutation compared with in those without co-mutation (38% versus 89%, p < 0.001). Conclusions Taking into account the small number of patients in this study, PFS in patients with EGFR co-mutation appeared significantly shorter, and response rate significantly lower, than in patients with a single mutation. Data from multipanel testing may identify subgroups of patients who are likely to respond poorly to standard treatment. Clarification of these subgroups may improve patient care

BRAF mutations in non-small cell lung cancer

Background: BRAF is a proto-oncogene encoding a serine/threonine protein kinase which promotes cell proliferation and survival. BRAF mutations are commonly seen in melanoma and papillary thyroid carcinoma. We aimed to investigate the prevalence and clinicopathological features of BRAF mutations in non-small cell lung cancer (NSCLC) cases submitted for routine mutation testing at our institution. Methods: Mutation analysis for BRAF, EGFR and KRAS was performed using Sequenom MassARRAY platform with OncoCarta panel v1.0. Pathological features were reviewed and immunohistochemistry for BRAF V600E was also performed. Results: Seven out of 273 cases (2.6%) had BRAF mutations (three males and four females, median age 70 years, all smokers), with six adenocarcinomas and one NSCLC, not otherwise specified (NOS). All had wild-type EGFR and KRAS. The identified BRAF mutations were V600E (4/7, 58%), K601N, L597Q and G469V. BRAF V600E immunohistochemistry was positive in two cases with V600E and negative in one case with K601N (tissue available in three cases only). No significant difference in age or gender was found (BRAF mutant vs. wild-type). Conclusions: BRAF mutations occur in a small proportion of NSCLC that lack other driver mutations. The clinicopathological profile differs from that of EGFR mutant tumours. The potential benefits of BRAF-inhibitors should be investigated

Alterations of insulin-like growth factor-1 receptor gene copy number and protein expression are common in non-small cell lung cancer

Aims Insulin-like growth factor-1 receptor (IGF1R) is a tyrosine kinase membrane receptor involved in tumourigenesis that may be a potential therapeutic target. We aimed to investigate the incidence and prognostic significance of alterations in IGF1R copy number, and IGF1R protein expression in resected primary non-small cell lung cancer (NSCLC), and lymph node metastases. Methods IGF1R gene copy number status was evaluated by chromogenic silver in situ hybridisation and IGF1R protein expression was evaluated by immunohistochemistry in tissue microarray sections from a retrospective cohort of 309 surgically resected NSCLCs and results were compared with clinicopathological features, including EGFR and KRAS mutational status and patient survival. Results IGF1R gene copy number status was positive (high polysomy or amplification) in 29.2% of NSCLC, and 12.1% exhibited IGF1R gene amplification. High IGF1R expression was found in 28.3%. There was a modest correlation between IGF1R gene copy number and protein expression (r=0.2, p<0.05). Alterations of IGF1R gene copy number and protein expression in primary tumours were significantly associated with alterations in lymph node metastases (p<0.01). High IGF1R gene copy number and protein expression was significantly higher in squamous cell carcinomas (SCC) compared with other subtypes of NSCLC (p<0.05). There were no other associations between IGF1R status and other clinicopathological features including patient age, gender, smoking status, tumour size, stage, grade, EGFR or KRAS mutational status or overall survival. Conclusions High IGF1R gene copy number and protein overexpression are frequent in NSCLC, particularly in SCCs, but they are not prognostically relevant

Patterns of DNA mutations and ALK rearrangement in resected node negative lung adenocarcinoma

Background: Many studies have examined specific mutations in patients with resected lung adenocarcinoma across heterogeneous stages, comprising predominantly advanced/metastatic disease, but there is little data regarding the mutation profile of patients with early stage node negative disease. The aim of this study was to identify patterns of mutations in early stage node negative lung adenocarcinoma. Methods: A total of 204 patients who underwent resection for stage IB (sixth Ed American Joint Committee on Cancer) lung adenocarcinoma and received no neoadjuvant or adjuvant treatments were identified. Tumors were genotyped using the OncoCarta v1.0 kit (Sequenom, San Diego, CA) on the Sequenom MassARRAY platform. Fluorescence in situ hybridization for ALK rearrangement was also performed. Results: A total of 110 (54%) patients’ tumors harbored at least one mutation. KRAS, EGFR, PIK3CA, ALK, PDGFRA, AKT1, BRAF, FGFR1, and HRAS mutations were detected in tumors from 77 (37.7%), 29 (14.2%), 9 (4.4%), 2 (1%), 2 (1%), 1 (0.5%), 1 (0.5%), 1 (0.5%), and 1 (0.5%) patients respectively. Synchronous mutations (either comutations or double mutations) were identified in 18 (8.8%) patients. KRAS and PIK3CA mutations were associated with poorly differentiated tumors (p = 0.03; p = 0.02), whereas EGFR mutations were associated with well-differentiated tumors (p = 0.001). Five tumours contained EGFR mutations (one T790M and four exon 20 insertions), which are associated with resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs). Conclusions: Diverse patterns of mutations are seen in resected node-negative lung adenocarcinoma including an unexpectedly low rate of ALK rearrangement, EGFR mutations associated with resistance to EGFR-TKIs and a high rate of synchronous mutations. These data may influence the design of future adjuvant targeted therapy trials

EGFR mutant-specific immunohistochemistry has high specificity and sensitivity for detecting targeted activating EGFR mutations in lung adenocarcinoma

Aim We assessed the diagnostic accuracy of epidermal growth factor receptor (EGFR) mutant-specific antibodies for detecting two common activating EGFR mutations. Methods Immunohistochemical expression of mutation-specific antibodies against EGFR exon 19 deletion E746-A750 ((c.2235-2249del15 or c.2236-2250del15, p. Glu746-Ala750del) and exon 21 L858R point mutation (c.2573T>G, p.Leu858Arg) were assessed in a cohort of 204 resected early stage node negative lung adenocarcinomas, and protein expression was compared with DNA analysis results from mass spectrometry analysis. Results Of seven cases with L858R point mutation, six were positive by immunohistochemistry (IHC). There were three false positive cases using L858R IHC (sensitivity 85.7%, specificity 98.5%, positive predictive value 66.7%, negative predictive value 99.5%). All seven E746-A750 exon 19 deletions identified by mutation analysis were positive by IHC. Four additional cases were positive for exon 19 IHC but negative by mutation analysis. The sensitivity of exon 19 IHC for E746-A750 was 100%, specificity 98.0%, positive predictive value 63.6% and negative predictive value 100%. Conclusions Mutant-specific EGFR IHC has good specificity and sensitivity for identifying targeted activating EGFR mutations. Although inferior to molecular genetic analysis of the EGFR gene, IHC is highly specific and sensitive for the targeted EGFR mutations. The antibodies are likely to be of clinical value in cases where limited tumour material is available, or in situations where molecular genetic analysis is not readily available