Reproducibility of the NanoString 22‐gene molecular subgroup assay for improved prognostic prediction of medulloblastoma

摘要

Medulloblastoma is the most frequent malignant brain tumor in children. Four medulloblastoma molecular subgroups, MB SHH , MB WNT , MB GRP3 and MB GRP4 , have been identified by integrated high‐throughput platforms. Recently, a 22‐gene panel NanoString‐based assay was developed for medulloblastoma molecular subgrouping, but the robustness of this assay has not been widely evaluated. Mutations in the gene for human telomerase reverse transcriptase (h TERT ) have been found in medulloblastomas and are associated with distinct molecular subtypes. This study aimed to implement the 22‐gene panel in a Brazilian context, and to associate the molecular profile with patients’ clinical‐pathological features. Formalin‐fixed, paraffin‐embedded (FFPE) medulloblastoma samples ( n ?=?104) from three Brazilian centers were evaluated. Expression profiling of the 22‐gene panel was performed by NanoString and a Canadian series ( n ?=?240) was applied for training phase. h TERT mutations were analyzed by PCR followed by direct Sanger sequencing and the molecular profile was associated with patients’ clinicopathological features. Overall, 65% of the patients were male, average age at diagnosis was 18?years and 7% of the patients presented metastasis at diagnosis. The molecular classification was attained in 100% of the cases, with the following frequencies: MB SHH ( n ?=?51), MB WNT ( n ?=?19), MB GRP4 ( n ?=?19) and MB GRP3 ( n ?=?15). The MB SHH and MB GRP3 subgroups were associated with older and younger patients, respectively. The MB GRP4 subgroup exhibited the lowest 5‐year cancer‐specific overall survival (OS), yet in the multivariate analysis, only metastasis at diagnosis and surgical resection were associated with OS. h TERT mutations were detected in 29% of the cases and were associated with older patients, increased h TERT expression and MB SHH subgroup. The 22‐gene panel provides a reproducible assay for molecular subgrouping of medulloblastoma FFPE samples in a routine setting and is well‐suited for future clinical trials.