Clinical outcomes of advanced non-small cell lung cancer patients harboring distinct subtypes of EGFR mutations and receiving first-line tyrosine kinase inhibitors: brain metastasis and de novo T790M matters.

backgroundThe clinical features, survival outcomes and patterns of treatment failure of advanced non-small cell lung cancer (NSCLC) patients harboring distinct subtypes of EGFR mutations and receiving first-line EGFR tyrosine kinases inhibitor (TKIs) are not fully understood.

methodsConsecutive metastatic EGFR-mutant NSCLC patients receiving first-line EGFR-TKIs from October 2010 to March 2020 were enrolled and classified into two main groups based on the EGFR mutation subtypes: common mutation (L858R or exon 19 deletion), uncommon mutation (other EGFR mutations).

resultsOf the 1081 patients included, 74 (6.8%) harbored uncommon mutations. The baseline characteristics were generally balanced between the two groups, except that bone metastasis developed less frequently in patients with uncommon mutations (p = 0.02). No significant difference of survival outcomes was found between the two groups, except that among patients with baseline brain metastasis, the intracranial time to progression was significantly shorter in patients with uncommon mutations. Nine of the 17 patients with de novo T790M mutation received Osimertinib, whose overall survival tended to be longer than the remaining 8 patients without Osimertinib treatment (p = 0.08). The patterns of treatment failure were generally consistent between the two groups, except which patients with uncommon mutations had a higher risk developing progressive disease in the brain.

conclusionFirst-line EGFR-TKIs seemed to be less effective in controlling and preventing brain metastasis in patients with uncommon EGFR mutations and Osimertinib was associated with promising efficacy in patients with de novo T790M mutation, which warranted further validation.