Optimizing the identification of anaplastic oligodendroglioma patients that benefit from adjuvant PCV chemotherapy using the Illumina platform: A further report from EORTC study 26951.

Abstract

2011 Background: Adjuvant PCV chemotherapy improves overall survival (OS) in 1p/19q co-deleted grade 3 gliomas. Analyses of EORTC 26951 and RTOG 9402 suggest that other molecularly defined subsets of grade III tumors benefit as well. We previously identified a CpG-Island Hypermethylated Phenotype (CIMP+) as a candidate biomarker. This was further explored in a larger series using snap frozen (SF) or formalin fixed paraffin embedded (FFPE) tumor material, and compared to the value of 1p/19q, IDH1/2 and MGMT status. Methods: Methylation profiles were assessed using the Infinium HumanMethylation 27 or 450 BeadChip (Illumina). MGMT promoter methylation was re-assessed with a logistic regression model (MGMT-STP27) using probes cg1243587 and cg12981137 of the platform as described (Bady et al, Acta Neuropathol 2012;124:547-60). These probes correspond to area’s of the promoter correlated to MGMT protein expression. Previously, MGMT promoter methylation had been assessed using methylation specific multiplex ligation-dependent probe amplification (MS-MLPA). Results: Methylation profiling was conducted in 115 patients. CIMP status correlation between FFPE and SF was excellent (R2 0.96). In multivariate analysis, 1p/19q co-deletion and CIMP status were independent prognostic factors. Although 1p/19q status and IDH mutational status identify subgroups with more benefit of PCV chemotherapy, tests for interaction remain negative (p 0.25 and 0.33 respectively); MGMTstatus (MS-MLPA) had no impact (p = 0.70). However, CIMP status was of borderline predictive significance (p= 0.07), and MGMT-STP27 was of statistical significance (p = 0.003; HR unmethylated 1.61, 95% CI [0.71, 3.66], HR methylated 0.37, 95% CI 0.23, 0.61]. Conclusions: CIMP status and MGMT promoter methylation assessed with Illumina HumanMethylation BeadChips appear the most informative tests for identifying grade III glioma patients benefitting from the addition of PCV to RT. Validation in an independent dataset is required. Clinical trial information: NCT00002840.