TERT Promoter Mutation Detection in Cell-Free Tumor-Derived DNA in Patients with IDH Wild-Type Glioblastomas: A Pilot Prospective Study

Purpose: We conducted a pilot study to assess the feasibility and the potential implications of detecting TERT promoter ( TERT p)-mutant cell-free tumor-derived DNA (tDNA) in the cerebrospinal fluid (CSF) and plasma of glioblastoma patients. Experimental Design: Matched CSF and plasma samples were collected in 60 patients with glial tumors. The CSF collection was obtained during surgery, before any surgical manipulation of the tumor. The extracted tDNA and corresponding tumor DNA samples were analyzed for TERT p and isocitrate dehydrogenase ( IDH) hotspot mutations. In addition, the variant allele frequency (VAF) of TERT p-mutation in the CSF-tDNA was correlated with patients9 outcome. Results: Thirty-eight patients had TERT p-mutant, IDH wild-type glioblastomas. The matched TERT p mutation in the CSF-tDNA was successfully detected with 100% specificity and 92.1% sensitivity (n=35/38). In contrast, the sensitivity in the plasma-tDNA was far lower (7.9%). We concordantly observed a longer overall survival of patients with low VAF in the CSF-tDNA when compared to patients with high VAF, irrespective of using the lower quartile VAF (11.45%) [14.0 mo. (95%CI 10.3-17.6) vs. 8.6 mo. (95%CI 4.1-13.2), p=0.035], the lower third VAF (13%) [15.4 mo. (95%CI 11.6-19.2) vs. 8.3 mo. (95%CI 2.3-14.4), p=0.008] or the median VAF (20.3%) [14.0 mo. (95%CI 9.2-18.7) vs. 8.6 mo. (95%CI 7.5-9.8), p=0.062] to dichotomize the patients. Conclusions: This pilot study highlights the value of CSF-tDNA for an accurate and reliable detection of TERT p mutations. Furthermore, our findings suggest that high TERT p-mutation VAF levels in the CSF-tDNA may represent a suitable predictor of poor survival in glioblastoma patients.