Upfront Radiation Therapy Increases Severe Neurotoxicity Risk in Patients With Oligodendrogliomas

Area of Science:

• Neuro-oncology
• Radiation oncology
• Clinical outcomes research

Background:

• Oligodendrogliomas are rare malignant brain tumors with long median survivals after chemoradiation therapy.
• Longer patient lifespans increase the risk of adverse treatment effects.
• Understanding the long-term toxicity and survival outcomes of different radiation therapy (RT) strategies is crucial.

Purpose of the Study:

• To compare toxicity and survival outcomes between early upfront RT and deferred RT in patients with IDH-mutant and 1p19q-codeleted oligodendrogliomas.
• To evaluate the incidence of severe delayed toxicities, including radiation necrosis, stroke, and dementia.
• To determine if the timing of RT impacts progression-free or overall survival.

Main Methods:

• Retrospective review of 80 consecutive patients with IDH-mutant and 1p19q-codeleted oligodendrogliomas treated between 2005 and 2021.
• Patients were categorized based on treatment: upfront RT followed by chemotherapy, upfront chemotherapy with deferred RT, or no therapy.
• Severe toxicity was defined as stroke, dementia, and cerebral radiation necrosis.

Main Results:

• Forty-five percent of patients receiving early RT experienced severe delayed toxicity (radiation necrosis, stroke, or disabling dementia).
• Only 6.7% of patients receiving deferred RT experienced radiation necrosis without disability.
• No significant differences were observed in progression-free survival, overall survival, or mortality between the groups.

Conclusions:

• Upfront RT is associated with a substantially higher rate of severe delayed toxicity without improving survival outcomes.
• Deferring RT until disease progression is a viable strategy to reduce long-term treatment-related morbidity in oligodendroglioma patients.
• These findings support a paradigm shift towards delayed RT to improve quality of life for long-term survivors.