EPID-25. Molecular Epidemiology of Adult Diffuse Gliomas in the United States

INTRODUCTION US cancer registries recently started collecting data on brain molecular markers, providing for the first time population-based data on the molecular epidemiology of gliomas. However, the initial release contained a significant proportion of missing data, precluding complete incidence rate estimates. Additionally, disparities in reporting would lead to biased risk estimates for certain demographic groups. METHODS We used multiple imputation by chained equations to obtain the first complete incidence rate calculations and intermediate-term survival estimates for molecularly-defined adult-type diffuse gliomas in the US using data from the Surveillance, Epidemiology, and End Results Program Database from 2018 to 2021. RESULTS We identified 16,652 patients with gliomas. The incidence rates for IDH-mutant/1p19q-codeleted oligodendroglioma, IDH-mutant astrocytoma, IDH-mutant glioblastoma, IDH-wildtype astrocytoma, and IDH-wildtype glioblastoma were 0.32, 0.36, 0.12, 0.37, and 3.59 cases per 100,000 persons per year, respectively, with three-year survival rates of 84%, 77%, 43%, 25%, and 9% (P<.001). The incidence rate of IDH-wildtype gliomas rapidly increased with age, while that of IDH-mutant gliomas decreased (OR for IDH-wildtype in patients ≥40 years versus 20-39: 15.6 [95%CI 13.6-17.8]). Compared with non-Hispanic White populations (15.4% IDH-mutant), the percentage of IDH-mutant tumors was higher in Hispanic (22.3%, OR 1.58 [95%CI 1.39-1.79]), Asian/Pacific Islander (20.7%, OR 1.44 [95%CI 1.19-1.73]), and American Indian/Alaskan Native populations (28.4%, OR 2.19 [95%CI 1.34-3.58). There was no survival deficit for patients with IDH-mutant WHO grade 2 gliomas ages 40-59 versus 20-39 (93% versus 96%, P=.55). There were no significant survival differences by race and ethnicity after stratifying by IDH-status. CONCLUSION We provide the first complete incidence rate and intermediate-survival estimates for molecularly-defined gliomas in the US by age, sex, and race and ethnicity. We illuminate an alarming potential for over-treatment of younger and non-white patients based on treatment paradigms established by legacy clinical trials conducted in the pre-molecular era. These findings will be validated in the Central Brain Tumor Registry of the United States (CBTRUS) database.