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

Abstract

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), 123I‐meta‐iodobenzyl‐guanidine (123I‐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/mm2) and T2‐weighted sequences. 123I‐mIBG scintigraphy planar imaging (all patients), with additional 123I‐mIBG single‐photon emission computed tomography / computerized tomography (SPECT/CT) imaging (15 patients). Assessment ADC maps and 123I‐mIBG SPECT/CT images were coregistered to the T2‐weighted images. 123I‐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 (ADC25prc) was used over the entire tumor volume and the overall level of 123I‐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 ADC25prc values were found between different 123I‐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 ADC25prc values (P < 0.001); no association was found with pretreatment 123I‐mIBG avidity (P = 0.17). Completely nonviable tumors had significantly lower postchemotherapy ADC25prc 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 123I‐mIBG avidity and ADC values are complementary noninvasive biomarkers of therapeutic response in HR‐NB. Level of Evidence 4. Technical Efficacy Stage 3.

Comparison between whole‐body magnetic resonance imaging and whole‐body metaiodobenzylguanidine scintigraphy in the evaluation of primary tumor and metastases in neuroblastoma

“…Diffusion imaging may also be useful in detecting small metastases in solid viscera, especially the liver. [10][11][12] Currently, WB-MRI, a noninvasive imaging method, can be used to diagnose and stage tumors, as well as to assess therapeutic responses in pediatric solid tumors and lymphomas. 4,5 The availability of studies on the role of WB-MRI in neuroblastoma is still limited.…”

Know thy tumour: Biomarkers to improve treatment of molecular radionuclide therapy

“…Other non-nuclear imaging biomarkers should not be overlooked, such as recent advancements with MRI diffusion weighted imaging MRI (MRI-DWI). Apparent diffusion coefficients with MRI-DWI have been associated with significant post-chemotherapy tumour reductions where [ 123 I]mIBG had no significant association [103]. While these studies have not yet been applied to [ 131 I]mIBG MRT, the association between diffusion and effective delivery of MRT agents such as [ 177 Lu]Lu-DOTATATE have been found preclinically [104,105].…”

123I-Meta-Iodobenzylguanidine Single-Photon Emission Computerized Tomography/Computerized Tomography Scintigraphy in the Management of Neuroblastoma

“…[ 8 22 ] mIBG avidity of the primary tumor does not correlate with restricted diffusion at diffusion-weighted MRI (DW-MRI). [ 23 ]…”

“…[ 24 ] In this context 123 I-mIBG SPECT/CT often shows heterogeneous mIBG avidity within the primary tumor mass: nodules of viable tumor on MRI can exhibit a high, moderate, low or absent mIBG avidity on SPECT/CT. [ 23 ] This is relevant when molecular radiotherapy with 131 I-mIBG is contemplated: given the different degree of mIBG avidity (or no avidity at all), the uptake of the therapeutic radiopharmaceutical within the neuroblastoma lesions will be higher or lower, or completely absent, with more or less or no response. [ 25 ] Initial attempts at testing the avidity of the primary neuroblastoma to different imaging biomarkers (in particular, 123 I-mIBG targeting NE analog re-uptake, and 68 Ga-DOTATATE targeting somatostatin receptors) have shown that some neuroblastoma cells show avidity for one tracer and not for the other, and vice versa: this finding needs further evaluation as it may have implications for molecular radiotherapy in that two combined therapeutic radiopharmaceuticals (for example, 131 I-mIBG and 177 L u-DOTATATE) may potentially yield a better response than one.…”

“…Residual 123 I-mIBG avidity in the primary tumor does not correlate with restricted diffusion at DWI-MRI after chemotherapy. [ 23 ]…”