Osimertinib is a third-generation, irreversible, oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that potently and selectively inhibits both EGFR sensitizing mutation and EGFR T790M and has demonstrated efficacy in non-small cell lung cancer (NSCLC) central nervous system metastases.
Compared with chemotherapy, molecular testing in plasma and tissue followed by osimertinib treatment yielded an additional 0.359 and 0.313 QALYs in the entire U.S. population and the population of those with central nervous system metastases and an EGFR T790M mutation.
Osimertinib had significantly greater efficacy than platinum therapy plus pemetrexed in patients with T790M-positive advanced non-small-cell lung cancer (including those with CNS metastases) in whom disease had progressed during first-line EGFR-TKI therapy.
Here we report two cases of gefitinib- or erlotinib-pretreated NSCLCs with a T790M mutation-positive (as assessed on plasma through the therascreen EGFR test) disease and untreated, asymptomatic central nervous system metastases that responded to treatment with osimertinib.
We analyzed DNA samples isolated from paraffin-embedded tissue from CNS metastases for T790M mutations using real-time PCR and TaqMan probe against the T790M mutant sequence.