MPTH-10. LOW INCIDENCE OF R132H IDH-1 MUTATIONS IN LONG TERM GLIOBLASTOMA SURVIVORS

Abstract

BACKGROUND: Long term survival from glioblastoma multiforme [GBM] is rare. Despite aggressive surgery, chemotherapy and radiation, median survival time is 14.6 months. Nevertheless, small fractions of patients (<20%) survive longer than 36 months and are considered long-term survivors. Established survival predictors include younger age at diagnosis, higher performance scores, greater extent of surgical resection, and chemoradiation therapy. Recently, tumors expressing isocitrate dehydrogenase [IDH] gene mutations have been associated with increased chemotherapy sensitivity and longer survivals. However, several investigators report low IDH mutation frequency in long term survivor cohorts. METHODS: We retrospectively identified long term GBM survivors from our single-institution database diagnosed between 2005-2013. We excluded patients progressing from lower grade gliomas. We reviewed patient characteristics, including clinical presentation, imaging features, surgical resection, pathology findings, R132H IDH1 immunostains, treatment, and outcomes of these long-term survivors. All initial pathologies were re-reviewed by an independent pathologist. RESULTS: 308 patients were diagnosed during the study period, of whom 30 (9.7%) survived longer than 36 months. Thirteen of these patients are still alive, five off therapy and two on hospice. One patient was lost to follow-up after 43 months. Median overall survival of the cohort was 42 months (range 36-116). The median age of long term survivors at diagnosis was 55.9 years (range 29.1-81.3), 17 (57%) were male, and median KPS at diagnosis was 90 (range 70-90). Seizures were the presenting complaint in 14 patients. Three patients underwent stereotactic biopsy, 24 gross total resection, and 3 subtotal resection. All but one patient received chemoradiation treatment as initial therapy. Five tumors contained IDH1 mutations. CONLUSIONS: Long term survival of patients is generally associated with younger age, higher KPS, gross total resection, seizures at presentation, IDH mutation, and cortical location. While many of our patients possessed these characteristics, the reasons for their long term survivals remain unclear.