Association of a diffuse phenotype on MRI with shorter overall survival in patients with astrocytoma CNS WHO grades 2 and 3

OBJECTIVE Gliomas can appear radiologically diffuse or sharply delineated on MRI. This can be quantified by the T1/T2 ratio, a quotient of the T1 hypointense to T2 hyperintense tumor volume. In patients with CNS WHO grade 2 and 3 isocitrate dehydrogenase ( IDH )–mutant astrocytomas, resectability has been shown to be limited in cases of low T1/T2 ratios, that is, in diffusely appearing astrocytomas. The authors set out to investigate if a diffuse phenotype on MRI is associated with overall survival beyond resectability. METHODS Retrospective data sets from two university hospitals (Sahlgrenska University Hospital, Gothenburg, Sweden; LMU University Hospital, Munich, Germany) were screened for patients diagnosed with 2021 CNS WHO grade 2 and 3 astrocytomas by biopsy between 2003 and 2021. Patients having undergone tumor resection were excluded. Tumor volumes were segmented and the T1/T2 ratio was calculated. Propensity score matching (nearest-neighbor matching, 1:1) was used. RESULTS One hundred nineteen patients with CNS WHO grade 2 (n = 77, 65%) or grade 3 (n = 42, 35%) IDH -mutant astrocytomas were included in the study. In unadjusted analyses, survival was not significantly shorter in patients with a T1/T2 ratio ≤ 0.33 (144 vs 126 months; HR 0.61, 95% CI 0.34–1.1; p = 0.09). Propensity score matching (Karnofsky Performance Status, CNS WHO 2021 grade, contrast enhancement on MRI, and T2 tumor volume) yielded 29 pairs. Here, significantly shorter overall survival was observed in patients with a T1/T2 ratio ≤ 0.33 (160 vs 132 months; HR 0.44, 95% CI 0.19–1.00; p = 0.05). In multivariate analysis, only the T1/T2 ratio persisted as a prognostic factor (HR 0.48, 95% CI 0.25–0.92; p = 0.03). CONCLUSIONS A diffuse phenotype on MRI seems to be associated with shorter survival times in patients with CNS WHO grade 2 and 3 astrocytomas. These findings warrant further investigation in prospective data sets.