Rhombencephalitis and longitudinal extensive myelitis associated with dinutuximab use in high-risk neuroblastoma.

BACKGROUND: Dinutuximab is a monoclonal antibody that targets the GD2 antigen used in the treatment of high-risk neuroblastoma. Dinutuximab-associated rhombencephalitis and myelitis is a rare, steroid-responsive, serious, but reversible pathology. To date, three transverse myelitis cases and one rhombencephalitis case due to dinutuximab have already been reported. Moreover, a recently published article identified five inflammatory CNS demyelination cases (four myelitis and one rhombencephalitis). We present a 5-year-old patient with rhombencephalitis and myelitis following dinutuximab-beta treatment. CASE: A 5-year-old patient with a left-sided retroperitoneal mass infiltrating the left kidney and multiple lytic bone lesions was diagnosed with neuroblastoma with a percutaneous biopsy from the abdominal mass. Surgery was performed after a prominent treatment response was detected on the abdominal CT. Radiotherapy was applied to the abdomen. While she was still undergoing maintenance treatment with 13-cis retinoic acid, a metaiodobenzylguanidine (MIBG) scan detected new bone lesions, and brain MRG identified pachymeningeal involvement. A new chemotherapy regimen was started and decreased MIBG uptake was seen in all previous bone lesions. However, newly developed eighth rib metastasis was seen in the following MIBG scan. Autologous stem cell transplantation was done. Soon after, dinutuximab-beta, together with temozolomide and irinotecan, was initiated. Following the third cycle hypotension, somnolence, paraparesis, and unilateral fixed dilated pupil were developed. Afterward, hemiballismus-like irregular limb movements were observed. Work-up studies were unremarkable, except for hypodensity in the brain stem on the brain CT. MRI revealed T2 hyperintensity of the brainstem and spinal cord extending from the cervicomedullary junction to the T7 level. Moreover, incomplete contrast enhancement and facilitated diffusion were observed. Imaging findings suggested demyelination. Steroids and intravenous immune globulin (IVIG) treatment were initiated. Both imaging abnormalities and clinical symptoms resolved partially at one month and disappeared at six months. CONCLUSIONS: Awareness of the radiological findings of dinutuximab toxicity will lead to prompt diagnosis and treatment.

Different Attenuation Models of Diffusion-Weighted MR Imaging for the Differentiation of Benign and Malignant Musculoskeletal Tumors.

BACKGROUND: Several functional imaging techniques, including monoexponential diffusion-weighted imaging (m-DWI), intravoxel incoherent motion (IVIM), and diffusion kurtosis (DK) imaging, have been used in differentiating benign and malignant musculoskeletal tumors. Combining all three techniques in the same study population may improve differentiation. PURPOSE: To compare the diagnostic performance of m-DWI, IVIM, and DK models and their combinations in differentiating benign and malignant musculoskeletal tumors. STUDY TYPE: Prospective. POPULATION: Fifty patients with benign and malignant musculoskeletal tumors divided into nonmyxoid and nonchondroid and myxoid and/or chondroid subgroups. FIELD STRENGTH/SEQUENCE: A 1.5 T/m-DWI, IVIM, and DK single-shot spin-echo echo-planar sequences. ASSESSMENT: Minimum and volumetric values of apparent diffusion coefficient (ADC), pure molecular diffusion (Divim ), pseudodiffusion (D*), perfusion fraction (f), diffusion coefficient for kurtosis model (DK ), and Kurtosis (K) were compared between all benign and malignant tumors. Subgroup analysis was also performed for nonmyxoid and nonchondroid and myxoid and/or chondroid tumors. STATISTICAL TESTS: Independent samples t-test, Mann-Whitney U test, intraclass correlation coefficient, ROC analysis, and logistic regression analysis. A P value < 0.05 was considered statistically significant. RESULTS: ADCmin , Divim-min , D*vol , DK-min, Kvol, and Kmin values showed statistically significant differences between all benign and malignant tumors and nonmyxoid and nonchondroid tumor subgroup. Kmin showed the highest diagnostic performance in differentiating benign and malignant tumors with AUCs of 0.760 for "all tumors" and 0.825 for the nonmyxoid and nonchondroid tumor subgroup. No significant differences were detected in m-DWI-, IVIM-, and DK-derived parameters for differentiating benign and malignant myxoid and/or chondroid tumors. Only three of 63 combinations of prediction models demonstrated a higher diagnostic performance than Kmin ; however, improvements were not significantly different. DATA CONCLUSION: ADCmin , Divim-min , D*vol , DK-min , Kvol , and Kmin values can be used to differentiate benign and malignant musculoskeletal tumors. Our findings suggest that the added value of multiparametric approach in such differentiation is not significant. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.

Diffusion-weighted imaging for the differentiation of Ewing sarcoma from osteosarcoma.

OBJECTIVE: The purpose of this study is to assess the ability of apparent diffusion coefficient (ADC) values in differentiating Ewing sarcoma and osteosarcoma. MATERIALS AND METHODS: This retrospective cross-sectional observational study included a total of 35 patients with a recent diagnosis of Ewing sarcoma (n = 13) and osteosarcoma (n = 22) who underwent conventional MRI and diffusion-weighted imaging (DWI). Three ADC measurements from the areas of the lowest diffusivity in ADC maps (ADCmin), and other areas with low diffusivity (ADCother), were made independently by two observers on pre-treatment MRI, and the means of these measurements were compared using independent samples t-test. Intraclass correlation coefficient was calculated for inter-observer agreement. RESULTS: There was a significant difference between the ADCmin (P < 0.001) and ADCother (P < 0.001) in Ewing sarcoma and osteosarcoma for both observers. For Ewing sarcoma and osteosarcoma, mean ADCmin was 0.566 ± 0.07 and 1.193 ± 0.33 × 10-3 mm2/s; 0.551 ± 0.08 and 1.182 ± 0.33 × 10-3 mm2/s; and mean ADCother was 0.813 ± 0.11 and 1.510 ± 0.35 × 10-3 mm2/s; 0811 ± 0.12 and 1.501 ± 0.33 × 10-3 mm2/s for observers 1 and 2, respectively. Inter-observer correlation coefficient for mean ADCmin was 0.994 and for mean ADCother was 0.995. CONCLUSION: Diffusion-weighted imaging and ADC values could be used in the differentiation of Ewing sarcoma and osteosarcoma in borderline cases.