MRI apparent diffusion coefficient reflects histopathologic subtype, axonal disruption, and tumor fraction in...

Area of Science:

• Neuro-oncology
• Radiology
• Pathology

Background:

• Distinguishing World Health Organization (WHO) grade II astrocytoma (AS) from oligodendroglioma (OD) is critical due to differing prognoses.
• Mixed oligoastrocytomas (OAs) with 1p/19q codeletion share prognoses similar to OD, complicating classification.
• Previous studies suggested apparent diffusion coefficient (ADC) from diffusion tensor imaging (DTI) can differentiate AS and OD.

Purpose of the Study:

• To validate a previously established ADC-based criterion for differentiating AS and OD in an independent cohort.
• To investigate the performance of this criterion in mixed oligoastrocytomas (OAs) with varying 1p/19q chromosome status.
• To explore the association between ADC and tumor microstructure, including axonal disruption and tumor cell fraction.

Main Methods:

• Presurgical DTI scans were acquired, and ADC maps were generated.
• ADC colormaps guided targeted biopsies from distinct tumor regions.
• Biopsies were analyzed for SMI-31 (axonal disruption) and tumor cell fraction.

Main Results:

• The median normalized ADC distinguished OD from AS with 91% sensitivity and 92% specificity.
• 1p/19q codeleted OAs were classified as OD, while 1p/19q intact OAs were classified as AS.
• ADC showed positive associations with axonal disruption (SMI-31) and tumor cell fraction, with differing correlations based on glioma subtype.

Conclusions:

• The established ADC threshold effectively differentiates grade II OD and AS in a new cohort, including OAs with different 1p/19q statuses.
• ADC serves as a valuable imaging biomarker for distinguishing these glioma subtypes.
• ADC in grade II gliomas reflects underlying tumor biology, correlating with cellularity and axonal integrity.