Neurology Central

New method for classifying low and intermediate grade gliomas identified


A new method for classifying low and intermediate grade gliomas (LGGs) has recently been reported in the New England Journal of Medicine. This new approach – discovered utilizing molecular and genetic analysis – could lead to improvements in diagnosis, treatment and potentially patient outcomes, and also validates potential targets for future therapies.

In order to develop the new method, researchers from 44 federally designated cancer centers throughout the United States performed a genome-wide analysis of 293 adult LGGs from centers belonging to The Cancer Genome Atlas Research Network (National Cancer Institute, NIH, MD, USA). The findings of the analysis were then correlated with data associated with patients’ clinical outcomes.

It was discovered that the characteristics of one group of patients with LGGs with wild-type IDH had distinct scientific similarities to those of glioblastoma. The patients diagnosed with this type of LGG had median survival rates of approximately 1.7 years, which is only slightly longer than individuals with glioblastomas, who have a median survival rate of 1.1 years.

In comparison, patients diagnosed with the other two types of LGG (those with an IDH mutation and 1p/19q codeletion and those with an IDH mutation and no codeletion), had median survival rates of 8 and 6.3 years, respectively.

Previously, LGGs have been classified utilizing two primary factors: their presumed cell of origin, and the degree of severity, which is graded from I–IV based on the microscopic appearance of the glia, information which is then used to classify the disease in to one of six subtypes. It is this classification that determines oncologists’ treatment decisions. The new system indentified in this study decreases the number of subtypes to three and correlates more closely with patient outcomes.

Author Andrew Sloan from University Hospitals Case Medical Center (OH, USA) explained: “The new classification system has the potential to provide far more accurate assessments of brain tumors – known as LGGs – which in turn could enhance patients’ outcomes.”

In the current model, some patients with LGGs encountered symptoms as rapid and severe as those with glioblastomas. However, other patients diagnosed with LGGs had more encouraging prognoses, despite all the tumors having a similar appearance when observed under the microscope.

Sloan added: “Choice of therapy takes into account lineage and grade based on the microscopic appearance, which is necessarily subjective with variability between observers.”

Sloan concluded: “The findings demonstrate that these three groups of LGGs can be identified objectively by three different markers. While various centers have been using some of these markers for years, this study helps validate these three markers.”

Sources: The Cancer Genome Atlas Research Network. Comprehensive, Integrative Genomic Analysis of Diffuse Lower-Grade Gliomas. NEJM, DOI: 10.1056/NEJMoa1402121 (2015) (Epub ahead of print); University Hospitals Case Medical Center press release