Impact of EGFRA289T/V mutation on relapse pattern in glioblastoma.

BACKGROUND: Molecular factors influence relapse patterns in glioblastoma. The hotspot mutation located at position 289 of the extracellular domain of the epidermal growth factor receptor (EGFRA289mut) is associated with a more infiltrative phenotype. The primary objective of this study was to explore the impact of the EGFRA289 mutation on the pattern of relapse after chemoradiotherapy-based treatment of patients suffering from newly diagnosed glioblastoma. PATIENTS AND METHODS: An ancillary study from a prospective cohort of patients suffering from glioblastoma was conducted. All patients received radiotherapy and concomitant temozolomide. The population was divided into two groups according to EGFRA289 status (mutated versus wild-type). The primary endpoint was the overlap score (varying from 0 to 1) between the initial irradiated tumor volume (Vinit) and the relapse volume (Vr). Secondary endpoints explored the impact of EGFRA289mut on survival. RESULTS: One hundred twenty-eight patients were included and analyzed: 11% had EGFRA289mut glioblastoma (n = 14/128). EGFRA289mut glioblastomas had a relapse pattern that was more marginal than EGFRA289wt glioblastomas: a median overlap score Vinit/Vr of 0.96 was observed in the EGFRA289mut group versus 1 in the EGFRA289wt group (P = 0.05). Half of the population with EGFRA289mut tumor (n = 7/14) had a marginal relapse (i.e. overlap scoreVr/Vinit ≤ 0.95) compared to 23.7% (n = 27/114) in the EGFRA289wt group, P = 0.035. EGFRA289mut did not influence survival. CONCLUSION: We highlighted a link between the EGFRA289 mutation and the relapse pattern in glioblastoma. The independent role of EGFRA289mut and its clinical implication should now be explored in further studies.

Usefulness of circulating tumor DNA from cerebrospinal fluid in recurrent high-grade glioma.

Molecular documentation at relapse of high-grade glioma is an urgent need for patient care. A prospective pilot study was conducted to assess the rate of mutation detection using targeted deep sequencing on circulating tumor DNA from cerebrospinal fluid (CSF) after chemo-radiotherapy based treatment. Fifteen patients were included: 13 patients with glioblastoma, 1 patient with gliosarcoma and 1 patient with anaplastic astrocytoma. At progression, 10/15 patients (67%) had detectable mutations in the CSF. Among them, 5/10 patients harbored at least one common mutation between initial tumor and ctDNA. CSF protein level and cfDNA concentration were higher, although not significant, in the ctDNA positive group versus ctDNA negative group (1.17g/L vs. 0.79g/L). Molecular documentation obtained from ctDNA in CSF at the time of relapse is informative in around two-thirds of the patients.