TERT Promoter Mutation Analysis for Blood-Based Diagnosis and Monitoring of Gliomas

Liquid biopsy offers a minimally invasive tool to diagnose and monitor the heterogeneous molecular landscape of tumors over time and therapy. Detection of promoter mutations ( , ) in cfDNA has been successful for some systemic cancers but has yet to be demonstrated in gliomas, despite the high prevalence of these mutations in glioma tissue (>60% of all tumors). Here, we developed a novel digital droplet PCR (ddPCR) assay that incorporates features to improve sensitivity and allows for the simultaneous detection and longitudinal monitoring of two promoter mutations ( and ) in cfDNA from the plasma of patients with glioma. In baseline performance in tumor tissue, the assay had perfect concordance with an independently performed clinical pathology laboratory assessment of promoter mutations in the same tumor samples [95% confidence interval (CI), 94%-100%]. Extending to matched plasma samples, we detected mutations in both discovery and blinded multi-institution validation cohorts with an overall sensitivity of 62.5% (95% CI, 52%-73%) and a specificity of 90% (95% CI, 80%-96%) compared with the gold-standard tumor tissue-based detection of mutations. Upon longitudinal monitoring in 5 patients, we report that peripheral -mutant allele frequency reflects the clinical course of the disease, with levels decreasing after surgical intervention and therapy and increasing with tumor progression. Our results demonstrate the feasibility of detecting circulating cfDNA promoter mutations in patients with glioma with clinically relevant sensitivity and specificity.