Co-occurring genetic alterations predict distant metastasis and poor efficacy of first-line EGFR-TKIs in EGFR-mutant NSCLC.

Purpose: To determine the frequency of co-occurring genes in non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation and the predictive effect of co-mutations on the efficacy of EGFR tyrosine kinase inhibitors (EGFR-TKIs).

Methods: 54 patients with advanced NSCLC were tested for 422 clinically relevant genes by next-generation sequencing (NGS) before treatment. Among them, patients with EGFR mutation received first-line treatment of EGFR-TKIs. Progression-free survival (PFS) and objective response rate (ORR) were evaluated using Kaplan-Meier methods and compared between two groups using log-rank test.

Results: Among 24 EGFR mutant and 30 EGFR wild-type patients, co-mutation rate was lower in patients with EGFR mutation (62.5% [15/24] vs 93.3% [28/30], p = 0.005). There was lower frequency for co-alterations in BRAF (0% [0/24] vs 20% [7/30], p = 0.033), NF1 (4.2% [1/24] vs 30% [9/30], p = 0.038) and RAS-RAF-MAPK pathway genes (16.6% [4/24] vs 56.7% [17/30], p = 0.003) in EGFR mutation group. 24 patients with EGFR mutation received first-line treatment of gefitinib or erlotinib, with an ORR of 83.3% and a median PFS of 12.3 months (95% CI 10.00-14.60). Co-mutation was associated with shorter median PFS (10.2 months [95% CI 5.20-15.20] vs 15.3 months [95% CI 12.09-15.81]; HR 0.29 [95% CI 0.10-0.82]; p = 0.014) in EGFR mutation cohort. Among patients with EGFR mutation and distant metastasis, median PFS was decreased in those with co-mutations (6.3 months [95% CI 3.25-9.35] vs 22.0 months[95% CI 12.10-31.90]; HR 0.12 [95% CI 0.00-5.87]; p = 0.007) and frequency of PIK3CA (0% [0/12] vs 41.7% [5/12], p = 0.037) and PI3K/AKT/mTOR pathway genes (0% [0/12] vs 50% [6/12], p = 0.014) was lower.

Conclusion: The presence of co-mutations was lower in the EGFR mutation patients and reduces the efficacy of EGFR-TKI, especially in patients with distant metastases. Lower frequency of co-mutation in PIK3CA and PI3K/AKT/mTOR pathway genes may be responsible for promoting metastasis and limiting the efficacy of EGFR-TKIs.