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MA 11 - Emerging Diagnostic/Biomarkers in NSCLC (ID 668)
- Event: WCLC 2017
- Type: Mini Oral
- Track: Advanced NSCLC
- Presentations: 1
MA 11.03 - Gefitinib as First-Line Treatment of Plasma CtDNA EGFR Mutation-Positive NSCLC Detected by DdPCR: BENEFIT Study (CTONG1405) (ID 9278)
11:00 - 12:30 | Author(s): H. Gao
EGFR mutations in plasma circulating free tumor-derived DNA (ctDNA) as a predictor of EGFR TKI efficacy in patients with NSCLC requires validation in prospective studies. The large, prospective Phase II, single-arm, multicenter BENEFIT study (CTONG1405; NCT02282267) validated the efficacy of first-line gefitinib in EGFR mutation-positive NSCLC detected in plasma ctDNA using droplet digital PCR (ddPCR).
Patients with stage IV lung adenocarcinoma and plasma ctDNA EGFR-sensitizing mutations (exon 19 del or exon 21 L858R; by ddPCR) received first-line gefitinib (250 mg once-daily) until progressive disease (PD). Blood samples were collected every 8 weeks for dynamic EGFR analysis until PD. Primary endpoint was ORR. Secondary endpoints included PFS, DCR (Week 8), and analysis of baseline ctDNA samples by next-generation sequencing (NGS).
From December 2014-January 2016, 426 patients from 15 Chinese centers were screened: 391 had matched tissue and blood samples; 188 had ctDNA EGFR mutation-positive NSCLC and received gefitinib; and 183 had ≥1 post-baseline tumor assessment and plasma samples every 8 weeks until PD. At data cutoff (January 31, 2017), 152 patients had progressed. ORR was 72.1% (95% CI 65.0%,78.5%); DCR (Week 8) was 92.3% (95% CI 87.5%,95.8%); and median PFS was 9.5 months (95% CI 9.07,11.04). PFS was significantly shorter in the subgroup with baseline ctDNA de novo T790M mutations (5.0%, n=9) versus the EGFR-sensitizing mutations subgroup (5.6 vs 9.6 months, HR=2.60; 95% CI 1.32,5.12, p=0.004). In patients with Week 8 on-treatment plasma samples (n=167), the subgroup who showed EGFR mutation clearance in ctDNA by ddPCR (88%, 147/167) had longer PFS compared with those who did not (11.0 vs 2.1 months, HR=7.28; 95% CI 4.35,12.18, p<0.0001). The median time to emergence of acquired T790M mutation in plasma was 7.6 months. The T790M-positive rate increased from Week 24 (15.7%) to Week 48 (32.6%), with a corresponding increase in PD rate (24.7% at Week 24, 56.9% at Week 48). Among 180 patients with baseline NGS data, 21 (11.7%) harbored aberrations in additional oncogenic drivers (MET, ERBB2, KRAS, BRAF, RET, or ROS1) and tumor suppressors (TP53, RB1, and PTEN). This subgroup had worse PFS versus those with EGFR-sensitizing mutations alone (3.9 vs 13.0 months, HR=2.83; 95% CI 1.65,4.87, p=0.00016).
The BENEFIT study prospectively demonstrated that ctDNA-based EGFR mutation detection can be used to select patients for treatment with first-line gefitinib. Dynamic alterations in EGFR mutations could be used to predict efficacy and disease progression, ahead of radiological results.
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