Radiation-induced gliomas are a rare complication of cranial irradiation, occurring in less than 3% of cases 15 years post-treatment. Glioblastomas correspond to three-quarters of all radiation-induced gliomas.
The risk of developing a secondary CNS cancer following radiation exposure has been well established, especially with meningiomas. However, it is important to highlight that the absolute risk of developing a radiation-induced tumor after radiotherapy to the CNS remains relatively low, and usually, the overall benefits of the treatment outweigh this possible negative complication.
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Epidemiology
Studies have shown that the estimated cumulative risk for malignant brain tumors is 0.5-2.7% at 15 years post radiotherapy. 75% of all radiation-induced gliomas are glioblastomas and 25% are lower grade astrocytomas 3.
Pathology
Microarray gene expression profiling has been used experimentally to differ radiation-induced from spontaneous glioblastomas 1.
Criteria
Radiation-induced malignancies have been defined as those tumors which fulfill the following criteria 2:
- tumor in a previously irradiated area
- sufficient latency time between the original and new tumors
- new tumor must have distinct histology from the original
- no history of disease predisposing to tumor development
Radiographic features
There are no specific imaging features of the tumors themselves that differ radiation-induced from the sporadic gliomas. Please refer to the dedicated articles in the different types of gliomas for further details.