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The T1/T2 Ratio is Associated With Resectability in Patients With Isocitrate Dehydrogenase-Mutant Astrocytomas
Jonathan Weller1, Eddie de Dios2,3, Sophie Katzendobler1
1Department of Neurosurgery, LMU University Hospital, LMU Munich, München , Germany.
Background And Objectives:
Isocitrate dehydrogenase (IDH)-mutant astrocytomas central nervous system World Health Organization grade 2 and 3 show heterogeneous appearance on MRI. In the premolecular era, the discrepancy between T1 hypointense and T2 hyperintense tumor volume in absolute values has been proposed as a marker for diffuse tumor growth. We set out to investigate if a ratio of T1 to T2 tumor volume (T1/T2 ratio) is associated with resectability and overall survival (OS) in patients with IDH-mutant astrocytomas.
Methods:
Patient data from 2 centers (Sahlgrenska University Hospital, Center A; LMU University Hospital, Center B) were collected retrospectively. Inclusion criteria were as follows: pre and postoperative MRI scans available for volumetric analysis (I), diagnosis of an IDH-mutant astrocytoma between 2003 and 2021 (II), and tumor resection at initial diagnosis (III). Tumor volumes were manually segmented. The T1/T2 ratio was calculated and correlated with extent of resection, residual T2 tumor volume, and OS.
Results:
The study comprised 134 patients with 65 patients included from Center A and 69 patients from Center B. The median OS was 134 months and did not differ between the cohorts ( P = .29). Overall, the median T1/T2 ratio was 0.79 (range 0.15-1.0). Tumors displaying a T1/T2 ratio of 0.33 or lower showed significantly larger residual tumor volumes postoperatively (median 17.9 cm 3 vs 4.6 cm 3 , P = .03). The median extent of resection in these patients was 65% vs 90% ( P = .03). The ratio itself did not correlate with OS. In multivariable analyses, larger postoperative tumor volumes were associated with shorter survival times (hazard ratio 1.02, 95% CI 1.01-1.03, P < .01).
Conclusion:
The T1/T2 ratio might be a good indicator for diffuse tumor growth on MRI and is associated with resectability in patients with IDH-mutant astrocytoma. This ratio might aid to identify patients in which an oncologically relevant tumor volume reduction cannot be safely achieved.
Insights
The T1/T2 ratio on MRI may indicate diffuse tumor growth in IDH-mutant astrocytomas, impacting surgical outcomes. Lower ratios correlate with greater residual tumor volume and reduced extent of resection.
Area of Science:
- Neuro-oncology
- Radiology
- Oncology
Background:
- IDH-mutant astrocytomas (WHO grades 2-3) present heterogeneous MRI appearances.
- Pre-existing methods proposed T1/T2 discrepancy as a marker for diffuse tumor growth.
Purpose of the Study:
- To investigate the association between the T1/T2 tumor volume ratio and resectability and overall survival (OS) in IDH-mutant astrocytomas.
- To assess the T1/T2 ratio as a potential imaging biomarker for diffuse tumor infiltration.
Main Methods:
- Retrospective analysis of 134 patients with IDH-mutant astrocytomas from two centers.
- Manual segmentation of pre- and postoperative MRI scans for volumetric analysis.
- Calculation of the T1/T2 ratio and correlation with extent of resection, residual tumor volume, and OS.
Main Results:
- A T1/T2 ratio of 0.33 or lower was significantly associated with larger residual tumor volumes (17.9 cm³ vs 4.6 cm³) and lower extent of resection (65% vs 90%).
- The T1/T2 ratio did not directly correlate with overall survival (OS).
- Larger postoperative tumor volumes were independently associated with shorter survival times (HR 1.02).
Conclusions:
- The T1/T2 ratio may serve as an indicator of diffuse tumor growth in IDH-mutant astrocytomas on MRI.
- This ratio is associated with surgical resectability, potentially identifying patients where significant tumor reduction is challenging.
- The findings suggest the T1/T2 ratio could aid in surgical planning and prognostication.
