Prevalence of the EGFR T790M and other resistance mutations in the Australian population and histopathological correlation in a small subset of cases

We sought to review the prevalence of EGFR T790M and other EGFR mutations associated with either proven or probable tyrosine kinase inhibitor (TKI) resistance in the Australasian lung cancer population and to perform histopathological correlation in a subset of cases. Retrospective statistical analysis was performed on a set of targeted lung cancer gene mutation tests (FIND IT gene panel) performed at Sonic Healthcare during 2018 and early 2019. A total of 1833 lung adenocarcinoma tumour samples underwent somatic mutation testing. EGFR mutations were found in 28% (n=514) of patients, in whom 9.3% (n=48) T790M mutations were present (always combined with other EGFR mutations) and 4.8% (n=25) exon 20 insertions were found. We also compared the prevalence of EGFR mutations identified in our population with that of the four largest publicly available lung cancer cohorts (total n=576 samples). Finally, a subset of 38 samples of primary/and or metastatic lung adenocarcinomas from 23 patients, including five with serial biopsies, underwent detailed morphological analysis. No reproducible morphological correlates were found to be associated with T790M, exon 20 resistance mutations or rarer co-occurring EGFR mutations. Although this may be subject to referral bias towards patients with resistant disease, the incidence of EGFR and T790M mutations is higher in this series from an Australasian population than in other similar publicly available lung adenocarcinoma cohorts. We conclude that histopathological features cannot be used to predict the acquisition of EGFR resistance.

Comparative study on the mutational profile of adenocarcinoma and squamous cell carcinoma predominant histologic subtypes in Chinese non-small cell lung cancer patients

BACKGROUND

Distinction in the mutational profile between the common histological types, lung adenocarcinoma (LUAD) and squamous cell lung carcinoma (LUSC) has been well-established. However, comprehensive mutation profiles of the predominant histological subtypes within LUAD and LUSC remains elusive.

METHODS

We analyzed the mutational profile of 318 Chinese NSCLC patients of adenocarcinoma and squamous cell carcinoma predominant subtypes from seven hospitals using capture-based ultra-deep sequencing of 68 lung cancer-related genes.

RESULTS

Of the 318 NSCLC patients, 215 were diagnosed with LUAD and 103 with LUSC. Adenocarcinoma in situ and acinar adenocarcinoma were the most predominant subtypes of LUAD. On the other hand, keratinizing squamous cell carcinoma was the most predominant subtype of LUSC. Among the LUAD subtypes, EGFR sensitizing mutations were most prevalent in the invasive lepidic subtype. More than half of the patients with preinvasive adenocarcinoma in situ, minimally invasive, acinar, micropapillary and papillary subtypes were also EGFR-mutants. Patients with colloidal, invasive mucinous, and fetal subtypes had the least number of EGFR mutations. Moreover, KRAS mutations were prevalent in patients with invasive mucinous, colloid, enteric and solid subtypes. A total of 90% of the LUSC patients harbor mutations in TP53, wherein all patients except five with nonkeratinizing were TP53 mutants. PIK3CA amplifications were most prevalent in keratinizing, followed by basaloid and nonkeratinizing subtypes.

CONCLUSION

These data suggest that the mutational profiles among the predominant histological subtypes were very distinct, which provided a reliable tool to improve treatment decisions.