IDH wild-type grade 2 diffuse astrocytomas: prognostic factors and impact of treatments within molecular subgroups

Background: Prognostic factors and role of treatments are not well known in isocitrate dehydrogenase (IDH) wild-type (wt) grade 2 astrocytomas. The aim of this study was to define in these tumours clinical features, molecular characteristics and prognostic factors, with particular focus on molecular subgroups defined by cIMPACT-NOW update 3. Methods: We analysed 120 patients with confirmed diagnosis of grade 2 IDHwt astrocytoma according to WHO 2016, collected from 7 Italian centres between 1999 and 2017. Results: Median PFS and OS of the whole cohort were 18.9 and 32.6 months. Patients older than 40 years and patients with modest contrast enhancement on MRI had a shorter PFS and OS. Gross total resection yielded superior PFS and OS over non-gross total resection. PFS and OS of patients with either pTERT mutation or EGRF amplification were significantly shorter. The prognostic value of age, contrast enhancement on MRI and extent of surgery was different within the molecular subgroups. Gross total resection was associated with increased PFS (not reached versus 14 months, p = 0.023) and OS (117.9 versus 20 months, p = 0.023) in patients without EGFR amplification, and with increased OS in those without pTERT mutation (NR vs 53.7 months, p = 0.05). Conversely, for patients with EGFR amplification or pTERT mutation, gross total resection did not yield a significant survival benefit. Conclusion: Patients without EGFR amplification and pTERT mutation could be observed after gross total resection.