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.
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 .
Microarray gene expression profiling has been used experimentally to differ radiation-induced from spontaneous glioblastomas .
Radiation-induced malignancies have been defined as those tumors which fulfill the following criteria:
- 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
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.