The American Society for Radiation Oncology (ASTRO) has issued its first clinical guideline on the use of radiation therapy to treat patients with isocitrate dehydrogenase (IDH)-mutant grade 2 and grade 3 diffuse glioma. Published in Practical Radiation Oncology, the evidence-based recommendations outline the multidisciplinary planning and delivery techniques to manage this subset of central nervous system (CNS) tumors.
Gliomas are the most common type of primary malignant brain tumors in adults, accounting for nearly 8 in 10 of these tumors. In 2021, the World Health Organization (WHO) reclassified gliomas to reflect the discovery of new biomarkers, including mutations to the genes that encode isocitrate dehydrogenase (IDH) enzymes. IDH mutations occur in 70-80% of patients with lower-grade diffuse gliomas, and patients with IDH mutations tend to have longer survival than patients without them.
The change in WHO tumor grading raised questions about how best to treat patients who fell into the new classifications, explained Helen A. Shih, MD, MPH, Chair of the guideline task force, Director of the CNS & Eye Service in the Department of Radiation Oncology at Massachusetts General Hospital (MGH) and Medical Director of the MGH Proton Therapy Centers in Boston. “For patients diagnosed with low-grade glioma, clinical trials show improved survival outcomes with a variety of treatment approaches. The heterogeneity of patient cohorts in these trials and the use of a now-outdated tumor grading system also can make it difficult to draw conclusions for patient care without clear guidance based on the new WHO classification,” said Dr. Shih.
Studies on U.S. cancer care patterns show wide variation in the use of radiation therapy for patients with low-grade glioma, perhaps due to the lack of definitive overall survival benefit in randomized trials and few central recommendations, said Lia M. Halasz, MD, Vice Chair of the guideline task force, as well as Co-Director of the Alvord Brain Tumor Center and Director of the Radiation Oncology Residency Program at the University of Washington in Seattle. “We developed this guideline to help providers determine the best multidisciplinary management approaches for their patients, taking into account the various options available and implications for long-term outcomes,” said Dr. Halasz.
Recommendations in the guideline address the indications and optimal timing, as well as planning and delivery techniques, for radiation therapy in adult patients with IDH-mutant, WHO grade 2 and grade 3 glioma, including oligodendroglioma and astrocytoma. The guideline also addresses clinical management of adverse effects and includes an algorithm that summarizes the treatment paths. Key recommendations are:
First Guideline on Radiation Therapy for IDH-Mutant Glioma Issued by ASTRO . Appl Rad Oncol.