Dr. Zhu on Primary Resistance to Osimertinib in EGFR-Mutant NSCLC

You-cai Zhu, MD, PhD, Department of Thoracic Disease Diagnosis and Treatment Center, Zhejiang Rongjun Hospital, discusses primary resistance to osimertinib (Tagrisso) in EGFR-mutant non—small cell lung cancer (NSCLC).

At the 2019 European Lung Cancer Conference, Zhu presented data from a Chinese trial that examined a total of 117 patients with stage IIIb/IV EGFR-T790M NSCLC. Patients underwent tumor biopsies or liquid biopsies at the time of primary or acquired resistance to osimertinib. These samples included formalin-fixed paraffin-embedded samples, serum samples and serous effusions. Targeted next-generation sequencing was also used to assess patients’ genes.

Among those treated with osimertinib, 82.91% developed acquired resistance and 7.69% had primary resistance to the agent. According to the baseline specimens, 3 patients had MET amplification, 1 patient had BCL2L11 loss, 1 patient had ERBB2 amplification, 1 patient had a PTEN mutation, and 1 patient had an EZH2 mutation. Two patients had unknown status, suggesting that primary resistance to EGFR-T790M may be highly heterogenous, concludes Zhu.