Prognostic factors of grade 4 IDH-mutant astrocytoma.

e14019 Background: The data on the prognostic factors of grade 4 IDH-mutant astrocytoma remains limited since the 2021 update of the WHO classification of Central Nervous System tumors. This update recognizes the importance of molecular characteristics and confers a grade 4 diagnosis based on the presence of at least one of either necrosis, microvascular proliferation, or CDKN2A/B homozygous deletion. This study sought to determine the factors that impact prognosis of patients with grade 4 IDH-mutant astrocytoma. Methods: A retrospective review was performed on all patients diagnosed with grade 4 IDH-mutant astrocytoma on initial diagnosis (as defined by the 2021 WHO classification) across the three Mayo clinic campuses (Minnesota, Florida, Arizona) between 2002 and 2023. Datapoints collected included demographic, clinical, imaging, histological and molecular variables. Factors impacting survival outcomes (overall survival OS and progression free survival PFS) were evaluated using Cox regression models. Results: Sixty-two patients with grade 4 IDH-mutant astrocytoma were identified (43 based on histological criteria alone, 10 based on molecular criteria alone, and 9 based on both). The median age of the patients was 36 years, with 64.5% of the patients identified as male and 93.3% as white. 100% (n=58) of these patients received standard treatment after surgery (radiation/temozolomide). The median follow up was 3.3 years. The median PFS and OS were 3.2 and 6.9 years, respectively. The OS was impacted by an unfavorable tumor location (either tumor involving the midline or at least 3 brain lobes; 2.4 years vs. 12.8 years, HR 10.8 95% CI 3.29-35.6, p<0.001) and CDKN2A/B homozygous deletion (2.5 years vs. NR, HR=4.3 95% CI 1.5-12.3, p=0.0065). The PFS was impacted by an unfavorable tumor location (1.4 years vs. 4.6 years, HR=5.3 95% CI 2.21-12.7, p=0.002), CDKN2A/B homozygous deletion (1.4 years vs. 4.6 years, HR=6.2 95% CI 2.71-14.2, p<0.001) and MGMT promoter hypermethylation (4.6 years vs. 1.4 years, HR=0.369 95% CI 0.154-0.883, p=0.025). Age, sex, tumor size and the use of tumor-treating fields did not significantly affect survival outcomes. Using multivariable analyses, PFS remained significantly impacted by CDKN2A/B homozygous deletion (HR=11.3 95% CI 3.23-39.0, p=0.0001) and MGMT promoter hypermethylation (HR=0.243 95% CI 0.082-0.717, p=0.0104), but not by an unfavorable tumor location (p=0.819). Conclusions: Both CDKN2A/B homozygous deletion and MGMT status may independently influence the progression-free survival of patients with grade 4 IDH-mutant astrocytoma.