Association Between EGFR T790M Status and Progression Patterns During Initial EGFR-TKI Treatment in Patients Harboring EGFR Mutation.

BACKGROUND: Emergence of the T790M point mutation in exon 20 of the epidermal growth factor receptor (EGFR) is the most common mechanism of resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs). The aim of this study was to investigate the association between T790M mutation status and the progression patterns during EGFR-TKI treatment.

METHODS: We reviewed 181 patients with advanced non-small-cell lung cancer harboring EGFR mutation, who were evaluated for T790M mutation status after initial EGFR-TKI failure (gefitinib, erlotinib, or afatinib). We retrospectively investigated the patient characteristics, initial EGFR-TKI response, T790M mutation status, subsequent treatment after initial EGFR-TKIs, timing of re-biopsy, and progression patterns during the EGFR-TKI treatment.

RESULTS: After the resistance to the EGFR-TKIs, the T790M mutation was identified in 87 (48%) of 181 patients. Seventy-three (40%) patients had solitary lesion progression, and 108 (60%) had multiple lesion progression during the initial EGFR-TKI treatment. The prevalence of the T790M mutation was significantly greater in patients with solitary lesion progression than those with multiple lesion progression (58% vs. 24%; P < .0001). The overall response rate and progression-free survival on initial EGFR-TKIs were significantly better in patients who acquired T790M after failure of EGFR-TKIs than those without T790M (overall response rate, 80% vs. 60%; P = .0033 and progression-free survival, 11.4 vs. 9.3 months; P = .0050). The multivariate analysis showed that gender, initial EGFR-TKI response, and progression patterns were significantly associated with T790M mutation status.

DISCUSSION: The progression patterns during initial EGFR-TKIs and initial EGFR-TKI response are associated with the T790M mutation.