Grading Clear Cell Renal Cell Carcinoma Grade Using Diffusion Relaxation Correlated MR Spectroscopic Imaging

Abstract

Background: Clear cell renal cell carcinoma (ccRCC) is the most common subtype of RCC, and accurate grading is crucial for prognosis and treatment selection. Biopsy is the reference standard for grading, but MRI methods can improve and complement the grading procedure.

Purpose: Assess the performance of diffusion relaxation correlation spectroscopic imaging (DR-CSI) in grading ccRCC.

Study type: Prospective.

Subjects: 79 patients (age: 58.1 +/- 11.5 years; 55 male) with ccRCC confirmed by histopathology (grade 1, 7; grade 2, 45; grade 3, 18; grade 4, 9) following surgery.

Field strength/sequence: 3.0 T MRI scanner. DR-CSI with a diffusion-weighted echo-planar imaging sequence and T2-mapping with a multi-echo spin echo sequence.

Assessment: DR-CSI results were analyzed for the solid tumor regions of interest using spectrum segmentation with five sub-region volume fraction metrics (V_A , V_B , V_C , V_D , and V_E ). The regulations for spectrum segmentation were determined based on the D-T2 spectra of distinct macro-components. Tumor size, voxel-wise T2, and apparent diffusion coefficient (ADC) values were obtained. Histopathology assessed tumor grade (G1-G4) for each case.

Statistical tests: One-way ANOVA or Kruskal-Wallis test, Spearman's correlation (coefficient, rho), multivariable logistic regression analysis, receiver operating characteristic curve analysis, and DeLong's test. Significance criteria: P < 0.05.

Results: Significant differences were found in ADC, T2, DR-CSI V_B , and V_D among the ccRCC grades. Correlations were found for ccRCC grade to tumor size (rho = 0.419), age (rho = 0.253), V_B (rho = 0.553) and V_D (rho = -0.378). AUC of V_B was slightly larger than ADC in distinguishing low-grade (G1-G2) from high-grade (G3-G4) ccRCC (0.801 vs. 0.762, P = 0.406) and G1 from G2 to G4 (0.796 vs. 0.647, P = 0.175), although not significant. Combining V_B , V_D , and V_E had better diagnostic performance than combining ADC and T2 for differentiating G1 from G2-G4 (AUC: 0.814 vs 0.643).

Data conclusion: DR-CSI parameters are correlated with ccRCC grades, and may help to differentiate ccRCC grades.

Evidence level: 2 TECHNICAL EFFICACY STAGE: 2.

Keywords: T2 relaxation time; clear cell renal cell carcinoma; diffusion weighted imaging; multidimensional correlation MRI; tumor heterogeneity.