Differential Clinicopathological Features, Treatments and Outcomes in Patients with Exon 19 Deletion and Exon 21 L858R EGFR Mutation-positive Adenocarcinoma Non-small-cell Lung Cancer

The most common oncogenic driver in non-small-cell lung cancer (NSCLC) is the epidermal growth factor receptor () gene mutations that occur more frequently among Asians (30%-50%) as opposed to Caucasians (10%-15%). Lung cancer is one of the most prevalent cancers in India, with a reported adenocarcinoma positivity ranging between 26.1% and 86.9% in NSCLC patients. The prevalence of mutations in adenocarcinoma patients (36.9%) in India is higher than that of Caucasian patients and lower than that of East Asian patients. The exon 19 deletion (Ex19del) is more common than exon 21 L858R mutations in Indian patients with NSCLC. Studies have shown that the clinical behaviour of patients with advanced NSCLC differs between Ex19del and exon 21 L858R mutation status. In this study, we investigated the differences in clinicopathological features and survival outcomes after first line and second-line treatment with tyrosine kinase inhibitors ( TKIs) in NSCLC patients with Ex19del and exon 21 L858R mutation status. This study also focuses on the role and potential benefits of dacomitinib, a second-generation irreversible TKI, in patients with Ex19del and exon 21 L858R mutation-positive advanced NSCLC in Indian settings.