Comparison Between Diffusion‐Weighted MRI and (123)I‐mIBG Uptake in Primary High‐Risk Neuroblastoma

BACKGROUND: High‐risk neuroblastoma (HR‐NB) has a variable response to preoperative chemotherapy. It is not possible to differentiate viable vs. nonviable residual tumor before surgery. PURPOSE: To explore the association between apparent diffusion coefficient (ADC) values from diffusion‐weighted magnetic resonance imaging (DW‐MRI), (123)I‐meta‐iodobenzyl‐guanidine ((123)I‐mIBG) uptake, and histology before and after chemotherapy. STUDY TYPE: Retrospective. SUBJECTS: Forty patients with HR‐NB. FIELD STRENGTH/SEQUENCE: 1.5T axial DW‐MRI (b = 0,1000 s/mm(2)) and T(2)‐weighted sequences. (123)I‐mIBG scintigraphy planar imaging (all patients), with additional (123)I‐mIBG single‐photon emission computed tomography / computerized tomography (SPECT/CT) imaging (15 patients). ASSESSMENT: ADC maps and (123)I‐mIBG SPECT/CT images were coregistered to the T(2)‐weighted images. (123)I‐mIBG uptake was normalized with a tumor‐to‐liver count ratio (TLCR). Regions of interest (ROIs) for primary tumor volume and different intratumor subregions were drawn. The lower quartile ADC value (ADC(25prc)) was used over the entire tumor volume and the overall level of (123)I‐mIBG uptake was graded into avidity groups. STATISTICAL TESTS: Analysis of variance (ANOVA) and linear regression were used to compare ADC and MIBG values before and after treatment. Threshold values to classify tumors as viable/necrotic were obtained using ROC analysis of ADC and TLCR values. RESULTS: No significant difference in whole‐tumor ADC(25prc) values were found between different (123)I‐mIBG avidity groups pre‐ (P = 0.31) or postchemotherapy (P = 0.35). In the “intratumor” analysis, 5/15 patients (prechemotherapy) and 0/14 patients (postchemotherapy) showed a significant correlation between ADC and TLCR values (P < 0.05). Increased tumor shrinkage was associated with lower pretreatment tumor ADC(25prc) values (P < 0.001); no association was found with pretreatment (123)I‐mIBG avidity (P = 0.17). Completely nonviable tumors had significantly lower postchemotherapy ADC(25prc) values than tumors with >10% viable tumor (P < 0.05). Both pre‐ and posttreatment TLCR values were significantly higher in patients with >50% viable tumor than those with 10–50% viable tumor (P < 0.05). DATA CONCLUSION: (123)I‐mIBG avidity and ADC values are complementary noninvasive biomarkers of therapeutic response in HR‐NB. LEVEL OF EVIDENCE: 4. TECHNICAL EFFICACY STAGE: 3.