Droplet digital PCR assays quantifying patient-individualized TERT rearrangement breakpoint copies, ALK copy numbers, and allelic ALK p.R1275Q mutation frequencies were applied to longitudinally collected liquid biopsies (peripheral blood and bone marrow [BM] plasma, n = 44 biosamples), the mononuclear cell fraction from BM and matched tumor samples. The gene discussed is ALK; the disease is neoplasm.