Improving Noninvasive Classification of Molecular Subtypes of Adult Gliomas With Diffusion‐Weighted MR Imaging: An Externally Validated Machine Learning Algorithm

Background Genetic testing for molecular markers of gliomas sometimes is unavailable because of time‐consuming and expensive, even limited tumor specimens or nonsurgery cases. Purpose To train a three‐class radiomic model classifying three molecular subtypes including isocitrate dehydrogenase (IDH) mutations and 1p/19q‐noncodeleted (IDHmut‐noncodel), IDH wild‐type (IDHwt), IDH‐mutant and 1p/19q‐codeleted (IDHmut‐codel) of adult gliomas and investigate whether radiomic features from diffusion‐weighted imaging (DWI) could bring additive value. Study Type Retrospective. Population A total of 755 patients including 111 IDHmut‐noncodel, 571 IDHwt, and 73 IDHmut‐codel cases were divided into training ( n = 480) and internal validation set ( n = 275); 139 patients including 21 IDHmut‐noncodel, 104 IDHwt, and 14 IDHmut‐codel cases were utilized as external validation set. Field Strength/Sequence A 1.5 T or 3.0 T/multiparametric MRI, including T1‐weighted (T1), T1‐weighted gadolinium contrast‐enhanced (T1c), T2‐weighted (T2), fluid attenuated inversion recovery (FLAIR), and DWI. Assessment The performance of multiparametric radiomic model (random‐forest model) using 22 selected features from T1, T2, FLAIR, T1c images and apparent diffusion coefficient (ADC) maps, and conventional radiomic model using 20 selected features from T1, T2, FLAIR, and T1c images was assessed in internal and external validation sets by comparing probability values and actual incidence. Statistical Tests Mann–Whitney U test, Chi‐Squared test, Wilcoxon test, receiver operating curve (ROC), and area under the curve (AUC); DeLong analysis. P < 0.05 was statistically significant. Results The multiparametric radiomic model achieved AUC values for IDHmut‐noncodel, IDHwt, and IDHmut‐codel of 0.8181, 0.8524, and 0.8502 in internal validation set and 0.7571, 0.7779, and 0.7491 in external validation set, respectively. Multiparametric radiomic model showed significantly better diagnostic performance after DeLong analysis, especially in classifying IDHwt and IDHmut‐noncodel subtypes. Data Conclusion Radiomic features from DWI could bring additive value and improve the performance of conventional MRI‐based radiomic model for classifying the molecular subtypes especially IDHmut‐noncodel and IDHwt of adult gliomas. Level of Evidence 3. Technical Efficacy Stage 2.