Interestingly, Russo and colleagues noted that, at the time of tumor progression, circulating tumor DNA was found to have two novel NTRK1 mutations (NTRK1, p.G595R and p.G667C) that were not detectable in the plasma at the initiation of therapy, demonstrating evidence of acquired resistance to entrectinib.20 This evidence concerns the gene NTRK1 and neoplasm.