Diagnosis and Treatment Monitoring of a Patient with Gastrointestinal Stromal Tumor by Next‐Generation Sequencing and Droplet Digital Polymerase Chain Reaction Assay of a PDGFRA Mutation in Plasma‐Derived Cell‐Free Tumor DNA

AbstractIn patients with a suspected malignancy, standard‐of care management currently includes histopathologic examination and analysis of tumor‐specific molecular abnormalities. Herein, we present a 77‐year‐old patient with an abdominal mass suspected to be a gastrointestinal stromal tumor (GIST) but without the possibility to collect a tumor biopsy. Cell‐free DNA extracted from a blood sample was analyzed for the presence of mutations in GIST‐specific genes using next generation sequencing. Furthermore, liquid biopsies were used to monitor the levels of mutant DNA copies during treatment with a tumor‐specific mutation droplet digital PCR assay that correlated with the clinical and radiological response. Blood‐based testing is a good alternative for biopsy‐based testing. However, it should only be applied when biopsies are not available or possible to obtain because overall, in only 50%–85% of the cell‐free plasma samples is the known tumor mutation detected.

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