Do Long-Term Survivor Primary Glioblastoma Patients Harbor IDH1 Mutations?

Background Approximately 3 to 16% of glioblastoma multiforme (GBM) patients are considered long-term survivors (LTS: 3+ years). Objective Given the improved survival conferred by IDH1 mutations and the fact that these mutations are detected in 12% of newly diagnosed GBM cases, could long-term survivorship be explained by IDH1 mutation status? Our aim was to describe GBM LTS with IDH1 mutations and explore its association with overall survival (OS). Methods Records of 453 newly diagnosed adult GBM patients treated at a single institution from 2004 to 2010 were reviewed retrospectively for patients who survived at least 36 months postsurgery. Descriptive statistics for clinical characteristics, treatments received, and tumor biomarkers were reported. Estimates for progression-free survival (PFS) and OS were provided. Results Forty (8.8%) LTS GBM patients were identified, with a median age of 50 years and a median preoperative Karnofsky Performance Score (KPS) of 80. Most patients underwent near-total/gross-total resection (72.5%), postoperative radiation (97.5%), and adjuvant temozolomide (95%). PFS rates at 12, 36, 48, and 72 months were 67.5%, 40%, 32.7%, and 26.2%, respectively. Median OS has not yet been reached; however, the survival rate at 48 months was 62.1%. Among 35 patients with available tumor samples, only 8 (22.9%) had IDH1 mutations. No significant difference in median PFS was found between IDH1 mutation and wild-type patients (46.6 versus 26.3 months; p =0.45). Conclusions Less than a quarter of our patients' long-term survivorship was associated with favorable IDH1 status. Therefore, IDH1 status does not explain most of the long-term survivorship in the temozolomide era.