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We read with interest the manuscript entitled “Survival analysis for apparent diffusion coefficient measures in children with embryonal brain tumors”1 in Neuro-Oncology. We have several observations regarding this manuscript. Although the method described was found to be correlated with survival among adults with glioblastoma, adult glioblastoma constitutes a homogeneous group of tumor characteristics and patient presentations. In contrast, the “embryonal” patient population in this study is very heterogeneous and includes 9 supratentorial primitive neuroectodermal tumors, 40 medulloblastomas, and 9 supratentorial and infratentorial atypical teratoid/rhabdoid tumors (AT/RTs), neoplasms with markedly different tumor biology, histology, treatment regimens, and clinical prognoses. The significant variations in tumor molecular and biological characteristics and resultant patient prognoses among those with “embryonal” histologic findings have led experts in this area of clinical research to discourage grouping them into common categories. For example, prospective studies have shown that the presence of leptomeningeal metastasis and extent of tumor resection affect survival significantly for medulloblastomas, resulting in specific treatment recommendations based on these variables. These variations in treatment affect prognosis, whereas uniform treatment irrespective of these variables would lead to more variability in survival. Medulloblastomas, although analyzed as a single entity in this manuscript, have been recently recognized as a biologically heterogeneous group of at least 4 tumors that have different clinical outcomes.2 Furthermore, the rising incidence of AT/RTs in young children could at least partially explain why children younger than 3 years with embryonal brain tumors had a worse outcome.
We believe that the results of this study would be relevant to clinical practice if the study had been conducted among a more homogeneous cohort of patients prospectively enrolled in a clinical trial.
The authors do not have a conflict of interest.