Genetic alterations in adult diffuse glioma: occurrence, significance, and prognostic implications

Our understanding of diffuse glioma development and progression has expanded remarkably over the past decade. As the genetic alterations responsible for these tumors are identified, molecular models of glioma pathogenesis are emerging and hold great promise to explain the biologic mechanisms of these neoplasms. Although these models continue to evolve and remain highly simplified, some of the genetic alterations that they encompass appear to be prognostically useful. Among the astrocytic gliomas, age and tumor grade are the most powerful indicators of patient survival, however, a wide range of variability remains, particularly among the low- grade and anaplastic astrocytomas. Recent reports indicate that alterations of the PTEN tumor suppressor gene are independent predictors of overall survival for anaplastic astrocytoma patients, helping to distinguish the cases with behavior resembling their more malignant counterparts, the glioblastomas. Among the oligodendroglial tumors, alterations of the 1p and 19q chromosome arms have emerged as potentially powerful predictors of overall patient survival and in vivo chemotherapeutic response, while alterations of the p16/CDKN2A tumor suppressor gene suggest shorter overall survival. As our molecular models continue to improve, through functional analyses and the identification of additional genetic contributors, we will expand our capacity to more effectively prognose these patients and to design rational therapeutic strategies.