Prediction of Malignant Transformation of WHO II Astrocytoma Using Mathematical Models Incorporating Apparent Diffusion Coefficient and Contrast Enhancement

Abstract

Using only increasing contrast enhancement as a marker of malignant transformation (MT) in gliomas has low specificity and may affect interpretation of clinical outcomes. Therefore we developed a mathematical model to predict MT of low-grade gliomas (LGGs) by considering areas of reduced apparent diffusion coefficient (ADC) with increased contrast enhancement. Patients with contrast-enhancing LGGs who had contemporaneous ADC and histopathology were retrospectively analyzed. Multiple clinical factors and imaging factors (contrast-enhancement size, whole-tumor size, and ADC) were assessed for association with MT. Patients were split into training and validation groups for the development of a predictive model using logistic regression which was assessed with receiver operating characteristic analysis. Among 132 patients, (median age 46.5 years), 106 patients (64 MT) were assigned to the training group and 26 (20 MT) to the validation group. The predictive model comprised age (P = 0.110), radiotherapy (P = 0.168), contrast-enhancement size (P = 0.015), and ADC (P < 0.001). The predictive model (area-under-the-curve [AUC] 0.87) outperformed ADC (AUC 0.85) and contrast-enhancement size (AUC 0.67). The model had an accuracy of 84% for the training group and 85% respectively for the validation group. Our model incorporating ADC and contrast-enhancement size predicted MT in contrast-enhancing LGGs.

Characterization and clinical implications of different malignant transformation patterns in diffuse low‐grade gliomas

“…Bogdanska et al 41 (2017) proposed another model based on two cellular populations to describe the MT of LGG, while the complexity of the model restricted its application. For ease of use, Wong et al 15 built a model that combined apparent diffusion coefficient and contrast enhancement for detecting MT with an 84% accuracy rate. However, the model did not incorporate any molecular data.…”

“…First, not all high‐grade gliomas exhibit a palpable enhancement on MR images, 11 , 12 , 13 which can lead to an underestimation of the percentage of MT. Second, some LGGs with increased contrast enhancement have been histologically confirmed as grade 2, suggesting an obvious discordance between radiologic and pathologic findings 14 , 15 , 16 (Figure 1 ). Therefore, using contrast enhancement as a marker of MT has low specificity and limited accuracy and may even affect the interpretation of a patient's clinical outcome.…”