Characteristics and therapeutic strategies of radiation-induced glioma : case series and comprehensive review of the literature

Introduction: Secondary glioma after cranial irradiation, so-called radiation-induced glioma (RIG), is one of the serious late effects after cranial radiation therapy. However, clinical characteristics and ideal treatment strategies of these tumors are unclear. In this report, we analyzed our case series and conducted a comprehensive review to reveal the characteristics of RIG. Methods: We performed literature review and investigated individual cases. In our institutes, we found pathologically diagnosed 6 cases of RIG. Totally, 360 cases were analyzed. The latency periods from irradiation to development of RIG and median overall survival of RIGs were analyzed with Kaplan-Meier analysis. Spearman’s correlation test was used to determine the relationship between age at irradiation and the latency years. Results: The mean age at the development of RIG was 27.42±17.87 years and the mean latency periods was 11.35±8.58 years. Multiple gliomas were observed in 28.4%. WHO grade 3 and 4 RIGs were account for 93.3%. The latency periods showed significant shorter in higher WHO grade group (p=0.0366) and concomitant systemic chemotherapy group (p<0.0001). Age at irradiation was negatively associated with the latency periods (r=-0.2287, p=0.0219). RIG treated with radiotherapy showed longer survival compared to RIG treated without radiotherapy (p=0.0011). Conclusions: : Development in younger age, multiplicity, and high incidence of grade 3 and 4 are the clinical characteristics of RIG. Cranial irradiation at older ages, and concomitant chemotherapy were associated with a shorter latency period for the development of RIG. Radiation therapy is the feasible treatment option despite radiation-induced gliomas.