Prognostic value of circulating short-length DNA fragments in unresected glioblastoma patients

Abstract

Background: Liquid biopsy application is still challenging in glioblastoma patients and the usefulness of short-length DNA (slDNA) fragments is not established. The aim was to investigate slDNA concentration as a prognostic marker in unresected glioblastoma patients.

Methods: Patients with unresected glioblastoma and treated by radiochemotherapy (RT/TMZ) were included. Plasmas were prospectively collected at three times: before (pre-) RT, after (post-) RT and at the time of progression. Primary objective was to investigate the impact on survival of slDNA concentration [slDNA] variation during RT/TMZ. Secondary objectives were to explore the association between tumor volume, corticosteroid exposition and [slDNA]; and the impact of slDNA detection at pre-RT on survival.

Results: Thirty-six patients were analyzed: 11 patients (30.6 %) experienced [slDNA] decrease during RT/TMZ, 22 patients (61.1 %) experienced increase and 3 patients (8.3 %) had stability. Decrease of [slDNA] during RT/TMZ was associated with better outcome compared to increase or stability: median OS, since end of RT, of 13.2 months [11.4 - NA] vs 10.1 months [7.8 - 12.6] and 6.8 months [4.5 - NA], p = 0.015, respectively. slDNA detection at pre-RT time was associated with improved OS: 11.7 months in the slDNA(+) group versus 8.8 months in the slDNA(-) group, p = 0.004. [slDNA] was not associated with corticosteroids exposition or tumor volume. No influence on survival was observed for both whole cfDNA concentration or slDNA peak size.

Conclusion: [slDNA] decrease during radiochemotherapy phase is a favorable prognostic marker on OS for unresected glioblastoma patients. Larger and independent cohorts are now required.

Trial registration: ClinicalTrial, NCT02617745. Registered 1 December 2015, https://clinicaltrials.gov/ct2/show/NCT02617745?term=glioplak&draw=2&rank=1.

Keywords: Glioblastoma; Liquid biopsy; Plasma; Prognostic; Short-length DNA.

Fig. 1

Flow chart. cfDNA, cell-free DNA; slDNA, short-length DNA.

Fig. 2

Evolution of plasma cell-free DNA fragments during first-line treatment with radiotherapy-temozolomide (n=36). (A) Illustration of the three sampling times during the first line of treatment with radiotherapy/temozolomide. The progression time varies between patients and is defined by either tumor progression or recurrence according to RANO HGG criteria. Top right shows the workflow for cfDNA and slDNA analysis quantified by Tapestation®. (B) Overall concentration of short-length DNA fragments [slDNA] between pre-RT and post-RT times; as well as whole cell-free DNA concentration (C) and slDNA peak size (D). [slDNA] and [cfDNA] are presented using log scale y-axis. Grey lines represent the kinetic between pre- and post-RT per patient. cfDNA, cell-free DNA fragments; ctDNA, circulating tumor DNA; Iqr, interquartile range; RT, radiotherapy; slDNA, short-length DNA fragments; TMZ, temozolomide.

Fig. 3

Biological parameters during the first-line treatment. (A) Evolution of the slDNA concentration at all three sampling times. Concentration is represented by the mean with standard deviation (error bar). (B) The average concentration of cell-free DNA fragments [cfDNA] does not vary according to the three sampling times, neither does the average slDNA peak size (C). Pairwise Wilcoxon signed-rank test were realised for comparisons between pre-RT and post-RT or progression. pvalue significance: *=0.05; ns=non-significant.

Fig. 4

Survival curves in the slDNA cohort (n=36). The top-left Kaplan-Meier curve represents the overall survival curves comparison between patients experiencing slDNA increase (red, n = 22), decrease (green, n = 11) or stability (blue, n = 3) between pre-RT and post-RT time points. The top-right curve represents the same data using pooled patients with either increase or stability (violet, n = 25) or decrease slDNA (green, n = 11). The bottom curves represent the comparisons for progression-free survival with three groups (bottom-left) or pooled patients (bottom-right).

Fig. 5

Survival curves according to slDNA detection at the pre-RT time point. OS (A) and PFS (B) curves comparison are presented according to the detection of slDNA (slDNA(+), n = 25 versus slDNA(-), n = 11).