Nationwide Analysis of Initial Surgical Management for Newly Diagnosed Glioblastoma in Japan (2018-2023): Part 1....

Japan is undergoing rapid population aging, and glioblastoma is increasingly diagnosed in older adults. However, nationwide data on regional variation in age distribution, surgical volume, population-adjusted incidence, and treatment selection for newly diagnosed glioblastoma remain limited. Using anonymized data from the Japan Neurosurgical Database between 2018 and 2023, we analyzed patients with newly diagnosed glioblastoma who underwent initial tumor resection or biopsy and examined inter-prefectural heterogeneity in surgical practice patterns. Patient age was categorized into 5-year groups and stratified as <75 and ≥75 years, and prefecture-specific population data from the 2020 national census were used to calculate population-adjusted incidence.Across all 47 prefectures, the age distribution of surgically treated patients differed significantly from that of the general population, with older patients being consistently overrepresented. The magnitude of this difference varied substantially among prefectures, indicating marked regional heterogeneity in the age profile of patients undergoing surgical management. Significant inter-prefectural differences were also observed in the surgical volume, the population-adjusted incidence, and the balance between resection and biopsy. Patients undergoing biopsy were older than those undergoing resection, although the magnitude of this difference varied regionally. The proportion of tumor resection ranged widely across regions and persisted even among patients aged ≥75 years. Importantly, baseline functional status (modified Rankin Scale) and admission consciousness level (Japan Coma Scale) were largely comparable across the prefectures.These findings demonstrate substantial regional heterogeneity in the initial surgical management of glioblastoma in Japan that cannot be fully explained by population aging or patient condition alone.