Multiple high-grade gliomas: epidemiology, management, and outcome. A systematic review and meta-analysis.

Multiple high-grade gliomas (M-HGGs) are well--separated tumors, differentiated as multifocal (MF) and multicentric (MC) by their MRI features. The authors performed a systematic review and meta-analysis of literature examining epidemiology, clinical and radiological characteristics, management, and the overall survival from M-HGGs. According to PRISMA guidelines, a comprehensive review of studies published between January 1990 and January 2017 was carried out. The authors identified studies that examined the prevalence rate, clinical and radiological characteristics, treatment, and overall survival from M-HGGs in patients with HGG. Data were analyzed using a random-effects meta-analysis model. Finally, we systematically reviewed demographic characteristics, lesion location, and surgical and adjuvant treatments. Twenty-three studies were included in this systematic review. The M-HGGs prevalence rate was 19% (95% CI 13-26%) and the hazard ratio of death from M-HGGs in the HGGs population was 1.71 (95% CI 1.49-1.95, p < 0.0001). The MC prevalence rate was 6% (CI 95% 4-10%), whereas MF prevalence rate was 11% (CI 95% 6-20%) (p < 0.0001). There were no statistically significant differences between MF and MC HGGs in gender, lesion location, histological type, and surgical treatment. Survival analysis of MC tumors showed that surgical resection (gross total resection or subtotal resection) is an independent predictor of improved outcome (HR 7.61 for biopsy subgroup, 95% CI 1.94-29.78, p = 0.004). The prevalence of M-HGGs is approximately 20% of HGGs. The clinical relevance of separating M-HGGs in MF and MC tumors remains questionable and its prognostic significance is unclear. When patient status and lesion characteristics make it safe and feasible, cytoreduction should be attempted in patients with M-HGGs because it improves overall survival.