In patients with T790M mutation and progression of disease on osimertinib, is there any utility in checking peripheral blood cDNA for continued presence or absence of the T790M mutation?  

We strongly believe that there is utility in sending liquid biopsy for T790M positive patients progressing on osimertinib for several reasons. One reason is that there are now identifiable resistance mutations like C797S that may emerge. Depending on their allelic relationship to T790...