Radiation-induced malignant gliomas: a current review.

OBJECTIVE

Radiation-induced malignant gliomas (RIMGs) are known uncommon risks of brain irradiation. We describe 4 cases of RIMG that occurred at our institution and conduct the largest comprehensive review of the literature to characterize RIMGs better.

METHODS

Patients were identified through the PubMed database. Pearson R linear correlation test was used to evaluate the correlation between radiotherapy (RT) dose and age and latency period. Student t test was used to evaluate differences between latency periods for original tumor lesions. A normalized biologic equivalent dose analysis was performed to indicate the minimum and maximum radiation threshold for neoplasia. A Kaplan-Meier analysis was used to illustrate the overall survival curves.

RESULTS

The analysis included 172 cases from the PubMed database and 4 cases occurring at our institution. The median RT dose administered was 35.6 Gy, with the most common dosage ranges being 21-30 Gy (31%) and 41-50 Gy (21.5%). Median latency period was 9 years until diagnosis of RIMG, and RIMG occurred within 15 years in 82% of the patients. There was no correlation between the age of the patient at the time RT was administered (R(2) = 0.00081) or amount of RT (R(2) = 0.00005) and latency period for RIMG. The mean biologic equivalent dose for neoplasia of a RIMG was 63.3 Gy. The median survival of patients with RIMG improved over time (P = 0.004), with median survival of 9 months before 2007 and 11.5 months after 2007.

CONCLUSIONS

The risk of RIMG appears to be the same for all age groups, histologies, and RT dosages. Although the risk is low, patients should be aware of RIMG as a possible complication of brain irradiation.