Prevalence and breakdown of non-small cell lung cancer BRAF driver mutations in a large UK cohort.

BRAF inhibitors have been shown in clinical trials to improve patient outcomes in non-small cell lung cancer (NSCLC) patients harbouring selected BRAF driver mutations with a limited side effect profile, and therefore show potential as therapeutics in clinical practice. To utilise BRAF inhibitors effectively, understanding the prevalence of BRAF mutations within the local patient population is crucial, especially since NSCLC driver mutation rates have been observed to vary in different populations around the world. We interrogated a clinical archive of next generation sequencing (NGS) data representative of 7 years of routine UK practice in the National Health Service (NHS) to investigate the frequency of BRAF mutations, the breakdown of mutation classes and co-occurrence of other oncogenic driver mutations. Tissue biopsies from NSCLC cases referred to the Sarah Cannon Molecular Diagnostics Laboratory between January 2015 and February 2022 from multiple centres across UK were included in this study. Somatic mutation hotspots in relevant cancer-associated genes were analysed using amplicon/ion-torrent based NGS assays, and all NSCLC samples which harboured recognised BRAF driver mutations were identified through a combination of automated and manual data retrieval. Data regarding any other detected mutations and basic demographic information were also collected. Over the 7-year period, 5384 NSCLC samples were sequenced, with BRAF mutation identified in 185 (3.44%) of cases. These 185 cases represented a total of 73 Class I BRAF mutations (39.5%), 61 Class II mutations (33.0%) and 51 Class III mutations (27.6%). Of the 73 identified Class I mutations, 69 (69/185, 37.3%) were V600E and four (4/185, 2.16%) were non-V600E mutations. Five V600E cases had co-mutations (5/185, 2.7%). Various other known driver mutations were also identified in these 185 tumour samples, with KRAS (18/185, 9.73%) and PIK3CA (7/185, 3.78%) occurring at the highest frequency. This is the first large cohort-level study in the UK to profile the breakdown of BRAF-positive NSCLC biopsy samples using NGS in routine clinical practice. This study defines the proportion of NSCLC patients that may be expected to benefit from BRAF inhibitors and highlights the utility of using NGS as a diagnostic tool to improve targeted therapy stratification for NSCLC patients.

Performance evaluation of the Biocartis Idylla EGFR Mutation Test using pre-extracted DNA from a cohort of highly characterised mutation positive samples.

AIMS: Targeted therapies for non-small cell lung carcinoma (NSCLC) rely on the detection of specific genomic lesions, such as mutations within the epidermal growth factor receptor (EGFR) gene. The Biocartis Idylla platform and single-use EGFR mutation test cartridge is CE-IVD for use with formalin-fixed paraffin embedded (FFPE) tumour material, but can also function off-scope using extracted DNA as input material. This can expand the utility of the platform and potentially conserve valuable tissue. METHODS: We sought to evaluate the performance of this system to detect known EGFR mutations using extracted DNA at different input levels. 130 next generation sequencing-characterised NSCLC cases possessing EGFR mutations that were theoretically detectable by the Idylla system were selected. Replicate analyses were performed using the Idylla EGFR test with up to three different DNA input levels (20 ng, 50 ng and 250 ng). RESULTS: Considering only variants within the test manufacturer's specified scope, the Idylla EGFR test generated concordant findings for 90.77% of cases at 20 ng DNA input, 98.46% at 50 ng input and 100% at 250 ng input. Analyses with discordant findings all generated control quantification cycle (CQ) values greater than 23. Very low CQ values were associated with EGFR gene amplification. CONCLUSIONS: The Idylla EGFR Mutation Test can be used at least as well with pre-extracted DNA than with direct FFPE input. In cases with control CQ >23, reanalysis with an increased DNA input should ideally be undertaken. If this is not possible, the risk of false negative calls may be mitigated by manual review of the quantitative PCR data and/or by reflexing to alternative analysis options.

Prospective analysis of 895 patients on a UK Genomics Review Board.

BACKGROUND: The increasing frequency and complexity of cancer genomic profiling represents a challenge for the oncology community. Results from next-generation sequencing-based clinical tests require expert review to determine their clinical relevance and to ensure patients are stratified appropriately to established therapies or clinical trials. METHODS: The Sarah Cannon Research Institute UK/UCL Genomics Review Board (GRB) was established in 2014 and represents a multidisciplinary team with expertise in molecular oncology, clinical trials, clinical cancer genetics and molecular pathology. Prospective data from this board were collated. RESULTS: To date, 895 patients have been reviewed by the GRB, of whom 180 (20%) were referred for clinical trial screening and 62 (7%) received trial therapy. For a further 106, a clinical trial recommendation was given. CONCLUSIONS: Numerous challenges are faced in implementing a GRB, including the identification of potential germline variants, the interpretation of variants of uncertain significance and consideration of the technical limitations of pathology material when interpreting results. These challenges are likely to be encountered with increasing frequency in routine practice. This GRB experience provides a model for the multidisciplinary review of molecular profiling data and for the linking of molecular analysis to clinical trial networks.

Analysis of a large cohort of non-small cell lung cancers submitted for somatic variant analysis demonstrates that targeted next-generation sequencing is fit for purpose as a molecular diagnostic assay in routine practice.

AIMS: Targeted next-generation sequencing (tNGS) is increasingly being adopted as an alternative to single gene testing in some centres. Our aim was to assess the overall fitness and utility of tNGS as a routine clinical test in non-small cell lung cancer (NSCLC). METHODS: All NSCLC cases submitted to a single laboratory for tNGS analysis over a 3-year period were included. Rejection/failure rates and turnaround times were calculated. For reportable cases, data relating to observed genetic changes likely to be driving tumour growth and/or contributing to therapeutic resistance were extracted. The impact of varied referral site practices (tissue processing and sample format submitted) on analytical outcomes was also considered. RESULTS: A total of 2796 cases were submitted, of which 217 (7.8%) were rejected and 131 (5.1%) failed. The median turnaround time was seven working days. Of 2448 reported cases, KRAS, EGFR or other recognised driver mutations were observed in 35%, 17% and 5.4%, respectively. Of the remaining cases, 3.5% demonstrated significant incidental evidence of gene amplification. In 15% of EGFR-driven cases, evidence of an EGFR tyrosine kinase inhibitor resistance mechanism was observed. Potential concerns around the provision of slides or precut 'rolls' only (cf, formalin fixed paraffin embedded (FFPE) tissue blocks) as standard practice by certain referral sites were identified. CONCLUSIONS: A tNGS panel approach is practically achievable, with acceptable success rates and turnaround times, in the context of a routine clinical service. Furthermore, it provides additional clinically and analytically relevant information, which is not available from single gene testing alone.

The temporal dynamics of slightly deleterious mutations in Escherichia coli and Shigella spp.

The Shigella are recently emerged clones of Escherichia coli, which have independently adopted an intracellular pathogenic lifestyle. We examined the molecular evolutionary consequences of this niche specialization by comparing the normalized, directional frequency profiles of unique polymorphisms within 2,098 orthologues representing the intersection of five E. coli and four Shigella genomes. We note a surfeit of AT-enriching changes (GC-->AT), transversions, and nonsynonymous changes in the Shigella genomes. By examining these differences within a temporal framework, we conclude that our results are consistent with relaxed or inefficient selection in Shigella owing to a reduced effective population size. Alternative interpretations, and the interesting exception of Shigella sonnei, are discussed. Finally, this analysis lends support to the view that nucleotide composition typically does not lie at mutational equilibrium but that selection plays a role in maintaining a higher GC content than would result solely from mutation bias. This argument sheds light on the enrichment of adenine and thymine in the genomes of bacterial endosymbionts where purifying selection is very weak.

The rise and fall of deleterious mutation.

It is well established that selection is less efficient in small populations than in large ones. Here we review the impact of this effect by considering the gradual selective purging of deleterious mutation over time. We outline an approach to explore the dynamics of this process, and highlight its profound implications.