A Brief Report on Stable Disease among Amivantamab-treated Patients with Post-platinum Epidermal Growth Factor Receptor Exon 20 Insertion–Mutated Non-small Cell Lung Cancer: A Response-based Analysis from the CHRYSALIS Study

Background Amivantamab, an EGFR-MET bispecific antibody, is the first approved targeted therapy for EGFR Ex20ins NSCLC patients after prior platinum-based chemotherapy—a population with historically poor outcomes before amivantamab approval. As antitumor activity in single-arm studies typically focuses on responders, evaluation of outcomes in patients with stable disease (SD) as best response is of clinical interest. Patients and Methods Among 114 patients with post-platinum EGFR Ex20ins NSCLC in CHRYSALIS (NCT02609776; data cutoff: March 30, 2021), response was assessed by blinded independent central review via RECIST v1.1. Patients alive and receiving therapy at 12 weeks were grouped by response at this landmark: partial or complete response (PR+), SD, or progressive disease (PD). Progression-free survival (PFS) and overall survival (OS) by response cohort were determined using the Kaplan–Meier method; hazard ratios (HRs) and 95% confidence intervals (CIs) between response cohorts were calculated using Cox proportional hazards regression. Results Among patients alive and receiving therapy at 12 weeks (n=107), 42 (39%) had PR+, 52 (49%) had SD, and 13 (12%) had PD. Among patients with PR+ and SD, median PFS was 12.2 and 7.0 months, respectively. A corresponding improvement in OS was observed in patients achieving PR+ (median: not reached; HR vs PD=0.21 [95% CI: 0.08–0.54]) and SD (median: 23.0 months; HR vs PD=0.33 [95% CI: 0.14–0.77]), relative to those with PD (median: 14.0 months). Conclusion SD was observed in 49% of patients receiving amivantamab, with corresponding increases in OS that dramatically improved the prognoses of this patient population.