Noninvasive Assessment of IDH Mutational Status in World Health Organization Grade II and III Astrocytomas Using DWI and DSC-PWI Combined with Conventional MR Imaging

Abstract

Background and purpose: Isocitrate dehydrogenase (IDH) has been shown to have both diagnostic and prognostic implications in gliomas. The purpose of this study was to examine whether DWI and DSC-PWI combined with conventional MR imaging could noninvasively predict IDH mutational status in World Health Organization grade II and III astrocytomas.

Materials and methods: We retrospectively reviewed DWI, DSC-PWI, and conventional MR imaging in 42 patients with World Health Organization grade II and III astrocytomas. Minimum ADC, relative ADC, and relative maximum CBV values were compared between IDH-mutant and wild-type tumors by using the Mann-Whitney U test. Receiver operating characteristic curve and logistic regression were used to assess their diagnostic performances.

Results: Minimum ADC and relative ADC were significantly higher in IDH-mutated grade II and III astrocytomas than in IDH wild-type tumors (P < .05). Minimum ADC with the cutoff value of ≥1.01 × 10^-3 mm²/s could differentiate the mutational status with a sensitivity, specificity, positive predictive value, and negative predictive value of 76.9%, 82.6%, 91.2%, and 60.5%, respectively. The threshold value of <2.35 for relative maximum CBV in the prediction of IDH mutation provided a sensitivity, specificity, positive predictive value, and negative predictive value of 100.0%, 60.9%, 85.6%, and 100.0%, respectively. A combination of DWI, DSC-PWI, and conventional MR imaging for the identification of IDH mutations resulted in a sensitivity, specificity, positive predictive value, and negative predictive value of 92.3%, 91.3%, 96.1%, and 83.6%.

Conclusions: A combination of conventional MR imaging, DWI, and DSC-PWI techniques produces a high sensitivity, specificity, positive predictive value, and negative predictive value for predicting IDH mutations in grade II and III astrocytomas. The strategy of using advanced, semiquantitative MR imaging techniques may provide an important, noninvasive, surrogate marker that should be studied further in larger, prospective trials.

Fig 1.

A 52-year-old woman with a diffuse astrocytoma without IDH mutation. A, Axial T2WI demonstrates heterogeneous high signal intensity with indistinct borders on the left temporal lobe. B, Contrast-enhanced axial T1-weighted image demonstrates a lesion enhancement with blurred borders. C, A corresponding ADC map shows the tumor with a decreased ADC value (ADC_min = 0.684 × 10⁻³ mm²/s, rADC = 1.08). D, Correlative color CBV image shows elevated perfusion with the calculated rCBV_max of 3.10.

Fig 2.

A 50-year-old man with an anaplastic astrocytoma with an IDH mutation. A, Axial T2WI demonstrates heterogeneous high signal intensity with sharp borders on the right temporal lobe. B, Contrast-enhanced axial T1-weighted image demonstrates a nonenhancing lesion in the right temporal region. C, A corresponding ADC map shows the tumor with an increased ADC value (ADC_min = 1.456 × 10⁻³mm²/s, rADC = 2.51). D, Correlative color CBV image shows relatively low perfusion with the calculated rCBV_max of 1.86.

Fig 3.

Comparison of receiver operating characteristic curves of ADC_min, rADC, rCBV_max (A) and cMRI, DWI + DSC-PWI, and cMRI + DWI + DSC-PWI (B) in differentiating IDH-mutant grade II and III astrocytomas from wild types.