False-Positive Plasma Genotyping Due to Clonal Hematopoiesis

Area of Science:

• Oncology
• Genetics
• Molecular Diagnostics

Background:

• Plasma cell-free DNA (cfDNA) genotyping is a valuable tool in cancer care.
• Concerns exist regarding the accuracy of cfDNA assays.
• Most cfDNA originates from peripheral blood cells (PBC), which can harbor nonmalignant mutations.

Purpose of the Study:

• To investigate if clonal hematopoiesis (CH)-derived mutations in PBC cause false-positive results in plasma cfDNA genotyping.
• To assess the origin of detected mutations in cfDNA for non-small cell lung cancer (NSCLC) patients.

Main Methods:

• Patients with advanced NSCLC and cfDNA mutations (KRAS, JAK2, TP53) were identified.
• Peripheral blood cell (PBC) DNA was analyzed using droplet digital PCR (ddPCR) or next-generation sequencing (NGS).
• PBC genotyping was compared with cfDNA and, where available, tumor sequencing results.

Main Results:

• KRAS mutations detected in cfDNA were found to be present in PBC in two NSCLC cases.
• JAK2 V617F mutations identified in cfDNA were confirmed to originate from PBC in five cases.
• TP53 mutations detected in cfDNA were present in PBC but absent in tumor tissue in five cases, indicating CH origin.

Conclusions:

• A significant proportion of JAK2, some TP53, and rare KRAS mutations in cfDNA originate from CH, not the tumor.
• Clinicians must consider CH as a source of false-positive cfDNA genotyping results.
• Paired PBC genotyping may be necessary to accurately interpret cfDNA results and avoid misdiagnosis of occult malignancy.