[Increment of the incidence of glioblastoma following decrease in the incidence of brain tumors in 2000-2020: a population-based registry study].

Background: Prevalence and dynamics of certain morphological variants of neuroglial brain malignancies (ICD-10 C71) are unknown in the Russian Federation.
Objective: To assess the incidence of neuroglial brain malignancies in 2000-2020 considering individual records of morphologically verified cases in the cancer registry of the Arkhangelsk region.
Material and Methods: We analyzed overall and age-adjusted incidence of neuroglial brain malignancies in 2000-2020 considering morphological subtypes of tumor. Incidence of morphologically verified glioblastoma was assessed in detail taking into account gender, age and place of residence. Segmented regression analysis was used to assess the dynamics and significance of linear trends.
Results: In total, there were 1699 brain malignancies for the period from 2000 to 2020. Morphological verification was obtained in 1289 (76%) patients including 467 (27%), 92 (5%) and 307 (18%) ones with glioblastoma, anaplastic G3 glioma and G2 glioma, respectively. Percentage of glioblastoma and anaplastic gliomas increased from 23.4% and 3.9% in 2000 to 55.3% and 9.2% in 2020, respectively. Age-adjusted incidence for the entire C71 group decreased from 5.2 to 3.2 cases per 100,000 after 2015 (annual decline 7.1%). However, incidence of glioblastoma monotonously increased from 1.0 to 2.1 per 100,000 (annual increment 6.2%). Incidence was similar in men and women. Age-adjusted incidence was 50-70% higher among rural population.
Conclusion: Significant increase (>2 times) in the incidence of glioblastoma was found over the past twenty years. Probably, it is associated with improved diagnosis and registration of this disease. In-depth analysis of morbidity and survival of patients with rare neuroglial tumors is required.