Irradiation planning of a glioblastoma, Source: Klinikum der Universität München
Researchers have developed a new method of predicting disease progression in gliobastoma patients who have undergone standard treatment.
Roughly one fifth of all brain tumors diagnosed by doctors are gliobastomas. This aggressive and most common type of brain tumor continues to present doctors with huge challenges. Molecular markers could help them to make the right treatment decision but few prognostic factors for glioblastoma have been identified. The most important molecular marker, methylation of the O6-methylguanine transferase (MGMT) promoter region, has been described as a positive predictor for temozolomide-based radiochemotherapy. Up to now little research has been done into microRNA (miRNA - short sequences of RNA building blocks) changes in glioblastomas but a team has succeeded in identifying specific miRNAs that could serve as biomarkers for disease progression.
According to estimates, about 2,000 different miRNAs have been identified. In contrast to protein synthesis, the RNA is not needed to build molecules, many miRNAs are capable of preventing the production of certain proteins by destroying the respective RNA blueprint.
miRNAs indicate a poor prognosis
The researchers examined the composition of miRNAs in samples from 36 patients from whom tumor material had been removed during treatment, and whose subsequent course of treatment had been well documented.
“We repeatedly detected four miRNAs in tumors that had a particularly poor prognosis,” explains PD Dr. Karim-Maximilian Niyazi, senior physician at the University of Munich’s Grosshadern Hospital and first author of the study. Based on their data, the scientists calculated a risk score to distinguish two patient groups who were undergoing standard treatment and whose life expectancy varied by about five months. In order to corroborate their findings, they used data obtained from a further 58 independent samples. Here, too, they found that the composition of the miRNAs altered, the worse the prospects of a successful treatment outcome were.
“To date only few prognostic and predictive factors for glioblastoma have been identified,” says research team leader Dr. Kristian Unger, Deputy Head of the Radiation Cytogenetics Research Unit at the Helmholtz Zentrum München. “Our method could be used to identify candidates for alternative or intensified treatment options, as it is highly unlikely that patients with a high risk score would benefit from standard therapy.”
Since tumor tissue would generally be removed immediately, a corresponding analysis would be relatively easy to conduct and would not require any additional time or expense, the researchers note.
Whether the miRNAs have a malignant function in the cancer cells themselves or are merely an indirect marker is unknown.
