Fig. 6: Dynamics of ALK alterations over the course of disease.

a Comparison of allelic fractions of ALK mutations detected at diagnosis and relapse by NGS versus ddPCR. In two patients (P2 and P13), two different ALK mutations were detected in the same tumor samples. X indicates that no material was available, check marks indicate that mutations were detected by dideoxy-sequencing only, thus leaving their allelic fraction unknown. b Longitudinal monitoring of allelic fractions (as determined by ddPCR) of two different ALK mutations (R1275Q and F1174L) over the course of disease in an individual patient. The allelic fraction of the HRAS mutation occurring at week 275 was determined by panel NGS. ALK inhibitory treatment and the clinical course of disease are shown at the top, with arrowheads indicating progression or relapse of disease. Timepoints and localizations of biopsies are indicated by arrows; biopsies of metastasis were taken from the same maxillary metastasis, except the last biopsy, which was derived from bone marrow. c Schematic diagram for the clonal evolution of cancer cell populations reconstructed from whole-exome sequencing data in patient P13. T1–T6 represent the consecutive biopsies that were taken from the patient. Gray boxes highlight clones that were private to the respective biopsy. ALK and HRAS mutations are indicated as they appeared in chronological order. d Clonal composition of each biopsy. The ancestral clone C0 is illustrated on the left to indicate its presence in every biopsy. AF, allelic fraction; NGS, next generation sequencing; ddPCR, digital droplet PCR; mut, mutation; D, diagnosis; R, relapse; met, metastasis; PT, primary tumor; BM, bone marrow.