Abstract
BACKGROUND: Fractal dimension (FD) analysis of preoperative magnetic resonance imaging (MRI) scans offers a potential approach to quantify tumor structural complexity, but its utility for predicting tumor grade and cerebellar mutism syndrome (CMS) risk in pediatric posterior fossa tumors remains unestablished. This study aimed to evaluate FD's dual utility as a biomarker for tumor grading and CMS prediction in pediatric posterior fossa tumors. METHODS: A retrospective analysis was conducted on 247 pediatric patients diagnosed with posterior fossa tumors (97 with low-grade tumors and 150 with high-grade tumors; 74 with CMS and 173 without CMS) who underwent surgery at Beijing Children's Hospital and had preoperative MRI scans. FD was extracted using box-counting algorithms from both the tumor mask area (mFD) and the significant region area (sFD). The relationship between mFD and the World Health Organization (WHO) tumor grade was assessed, and the diagnostic performance of sFD in predicting CMS was also evaluated. RESULTS: mFD demonstrated a strong ability to differentiate between high- and low-grade posterior fossa tumors, with an area under the curve (AUC) of 0.80, sensitivity of 78%, and specificity of 75%. Significant differences in mFD were observed between WHO grades: grade 4 [0.88 (0.82-0.94)] > grade 3 [0.79 (0.68-0.89), P=0.03], grade 3 > grade 2 [0.68 (0.48-0.76), P=0.008], and grade 4 > grade 1/2 (both P<0.01), but not between grades 1 and 2 (P=1.00). For CMS prediction, sFD was significantly higher in the CMS group (0.60±0.24) versus the non-CMS group (0.46±0.22, P<0.001). The receiver operating characteristic (ROC) analysis for using sFD to predict CMS revealed a sensitivity of 67%, specificity of 61%, and an AUC of 0.66. Multivariable analysis confirmed sFD as an independent predictor of CMS [odds ratio (OR): 11.70, 95% confidence interval (CI): 3.10-43.90, P<0.001]. Subgroup analyses showed improved CMS prediction in females (AUC =0.73, sensitivity 83%) and non-midline tumors (AUC =0.72, specificity 80%). CONCLUSIONS: FD appears to be a promising biomarker for predicting both the grade of posterior fossa tumors and the likelihood of developing CMS in pediatric patients.