Epidemiological analysis of adult-type diffuse lower-grade gliomas and incidence and prevalence estimates of diffuse IDH-mutant gliomas in France

Background: The recent advent of anti-IDH therapies and changes in the WHO classification of gliomas implies estimating the number of patients who could benefit (or not) from anti-IDH treatment. As published data on the current incidence of different subtypes of IDH-mutant gliomas (based on the latest histomolecular WHO classification) are lacking in many countries. The present analysis aims to review the main factors impacting the incidence of gliomas and lower-grade gliomas and to estimate the incidence and prevalence of IDH-mutant gliomas in France.

Methods: Our analysis was based on data from the French Brain Tumor DataBase and literature.

Results: Case definition, recording methods, histological classifications, age, sex, ethnicity, ancestry, environment, genetics, etc., impact the incidence of gliomas overall and lower-grade gliomas. In France, for the year 2024, the incidence estimates of all gliomas and all adult-type diffuse IDH-mutant gliomas are 6.6/100,000 and 1/100,000 person-years, respectively. The incidence estimates of grades 2, 3, and 4 diffuse IDH-mutant gliomas are 0.5, 0.3, 0.2 per 100,000 person-years, respectively. Of note, the incidence estimate of grade 3 diffuse IDH-mutant glioma versus grade 2 or 4 is slightly more difficult to assess due to the possible variability in histological criteria to define tumor grade. The prevalence of diffuse IDH-mutant grade 2 glioma would be more than 6.57/100,000 persons.

Discussion/conclusion: Our epidemiological analysis provides estimates of potential number of patients, but large prospective real-world studies are required to determine the positioning of anti-IDH treatments among all therapeutic strategies [surgery(ies), chemotherapy(ies), radiotherapy(ies), clinical/radiological follow-up, etc.].