OS5.4 Characteristics of adult diffuse H3K27M-mutant gliomas at recurrence

Abstract BACKGROUND Adult diffuse H3K27M-mutant gliomas are rare and associated with a poor prognosis but could benefit in the next future from specific therapeutic strategies. In this context, the aim of the present study was to describe the characteristics of these tumors at recurrence. MATERIAL AND METHODS We retrospectively analyzed the characteristics of a series of 27 adult diffuse H3K27M-mutant gliomas at recurrence RESULTS Median age at diagnosis was 37 years. Initial treatment consisted of temozolomide radiochemotherapy (n=17, 62%), radiotherapy alone (n=1, 4%), chemotherapy alone (n=4, 15%), wait and see (n=1, 4%) and palliative care (n=4, 15%). Median PFS and median OS were 11 and 22 months in the whole series and 15 and 29 months in the patients who were treated with temozolomide radiochemotherapy. The pattern of recurrence could be analyzed in 19 patients. Ten patients (50%) demonstrated a local recurrence, five patients a local and distant recurrence (25%), two patients only a distant recurrence (10%) and two patients a leptomeningeal progression (10%). At recurrence, 15 patients received an oncological treatment that consisted of an alkylating chemotherapy (n=5), a bevacizumab based chemotherapy regimen (n=9) and of radiotherapy (n=1). Median PFS and OS after first recurrence in these patients were 6 and 14 months, respectively. An activating FGFR1 mutation was identified in 4 out of the 9 patients in whom it was assessed. CONCLUSION At recurrence, adult diffuse H3K27M-mutant gliomas are associated with a high rate of distant locations. A subset of patients harbor targetable FGFR1 activating mutations.