Radiation-induced gliomas: a comprehensive review and meta-analysis

By conducting a systemic search of the PubMed database, we performed a comprehensive literature review to characterize secondary gliomas following radiotherapy treatment and to determine the most appropriate treatment strategy. Our analysis included 296 cases of radiation-induced gliomas. The primary lesion was characterized as a hematological malignancy in 104 cases (35.1 %), pituitary adenoma in 35 (11.8 %), craniopharyngioma in 19 (6.4 %), medulloblastoma in 38 (12.8 %), germ cell tumor in 13 (4.3 %), low-grade glioma in 28 (9.4 %), cancer/sarcoma in 12 (4.0 %), scalp region disease in 15 (5.0 %), meningioma/schwannoma in 13 (4.3 %), metastatic brain tumor in 5 (1.6 %), and other types (e.g., arteriovenous malformations and angiomas) in 14 (4.7 %). The average age of onset for primary lesions was 16.0 +/- 15.8 years, and the average radiation dose delivered to the primary lesion was 37.6 +/- 20.0 Gy. Secondary gliomas could be divided into grade I (1), grade II (32), grade III (88), and grade IV (173) tumors. The median overall survival for all glioma cases was 11 months (95 % confidence interval [CI], 9-12), with a 2-year survival rate of 20.2 %. On multivariate analysis, combined modality treatment and the latency period from the radiotherapy treatment to the glioma diagnosis were variables associated with the overall survival of patients with grade III/IV secondary gliomas. For patients treated with cranial radiotherapy, the risk of secondary glioma incidence warrants a longer follow-up period beyond the standard time frame typically designated for determining the risk of primary tumor relapse. Moreover, combination therapy is a potential treatment option for radiation-induced gliomas.