Influence of Histological Subtype on Survival after Combined Therapy of Surgery and Radiation in WHO Grade 3 Glioma

World Health Organization (WHO) grade 3 glioma is one of the common brain tumors and has three main histological subtypes, including anaplastic astrocytoma (AA), anaplastic oligoastrocytoma (AOA) and anaplastic oligodendroglioma (AO). However, most previous studies have considered AOA and AO as one group because of the difficult differential diagnosis between AOA and AO. Therefore the prognostic difference among patients with these histological subtypes has been unclear. In this study, 68 patients with histologically proven WHO grade 3 glioma, consecutively received postoperative radiotherapy at the Gunma University Hospital, Japan, between 1983 and 2005, were investigated to assess the impact of histological subtype on the survival. The number of AA, AOA and AO patients was 41, 16 and 11, respectively. The mean and median follow-up periods were 72 and 48 months, respectively. The number of patients treated with gross total resection, partial resection and biopsy was 14, 38 and 16, respectively. The mean and median radiation doses were 58 +/- 5 Gy and 60 Gy, respectively. The 5-year overall survival rates of AA, AOA and AO were 21%, 38% and 80%, and median survival period were 16 months, 58 months and not reached, respectively. Univariate analysis showed that the histological subtype (P < 0.01) and extent of surgery (P < 0.01) were significant prognostic factors for survival. Selective comparison showed that overall survival of patients with AA was significantly worse than for those with AOA (P = 0.01) and AO (P < 0.01). The overall survival of patients with AO was better than for those with AOA; however, the difference was not statistically significant (P = 0.14). Multivariate analysis demonstrated that histological subtype, age and extent of surgery were the significant independent variable for survival (P < 0.01, P <0.01 and P = 0.04). In our study, histological subtype was one of the most important prognostic factors of WHO grade 3 glioma.