MRI features in children with desmoplastic medulloblastoma

Radiomics signature for the prediction of progression-free survival and radiotherapeutic benefits in pediatric medulloblastoma

PURPOSE

To develop and validate a radiomics signature for progression-free survival (PFS) and radiotherapeutic benefits in pediatric medulloblastoma.

MATERIALS AND METHODS

We retrospectively enrolled 253 consecutive children with medulloblastoma from two hospitals. A total of 1294 radiomic features were extracted from the region of tumor on the T1-weighted and contrast-enhanced T1-weighted (CE-T1w) MRI. Radiomic feature selection and machine learning modelling were performed to build radiomics signature for the prediction of PFS on the training set. Moreover, the prognostic performance of the clinical parameters was investigated for PFS. The Concordance index (a value of 0.5 indicates no predictive discrimination, and a value of 1 indicates perfect predictive discrimination) was used to measure and compare the prognostic performance of these models.

RESULTS

The radiomics signature for the prediction of the PFS yielded Concordance indices of 0.711, 0.707, and 0.717 on the training and held-out test sets 1 and 2, respectively. The radiomics nomogram integrating the radiomics signature, age, and metastasis performed better than the nomogram incorporating only clinicopathological factors (C-index, 0.723 vs. 0.665 and 0.722 vs. 0.677 on the held-out test sets 1 and 2, respectively), which was also validated by the good calibration and decision curve analysis. Further analysis demonstrated that patients with lower value of radiomics signature were associated with better clinical outcomes after postoperative radiotherapy (p < 0.001).

CONCLUSION

The radiomics signature and nomogram performed well for the prediction of PFS and could stratify patients underwent postoperative radiotherapy into the high- and low-risk groups with significantly different clinical outcomes.

Pediatric Posterior Fossa Medulloblastoma: The Role of Diffusion Imaging in Identifying Molecular Groups

BACKGROUND AND PURPOSE

The molecular groups WNT activated (WNT), Sonic hedgehog activated (SHH), group 3, and group 4 are biologically and clinically distinct forms of medulloblastoma. We evaluated apparent diffusion coefficient (ADC) values' utility in differentiating/predicting medulloblastoma groups at the initial diagnostic imaging evaluation and prior to surgery.

METHODS

We retrospectively measured the ADC values of the enhancing, solid portion of the tumor (EST) and of the whole tumor (WT) and performed Kruskal-Wallis testing to compare the absolute tumor ADC values and cerebellar and thalamic ratios of three medulloblastoma groups (WNT, SHH, and group 3/group 4 combined).

RESULTS

Ninety-three children (65 males) were included. Fifty-seven children had group 3/group 4, 27 had SHH, and 9 had WNT medulloblastomas. The median absolute ADC values in the EST and WT were .719 × 10^-3 and .864 × 10^-3 mm² /s for group 3/group 4; .660 × 10^-3 and .965 × 10^-3 mm² /s for SHH; and .594 × 10^-3 and .728 × 10^-3 mm² /s for WNT medulloblastomas (P = .02 and .13). The median ratio of ADC values in the EST or the WT to normal cerebellar tissue was highest for group 3/group 4 and lowest for WNT medulloblastomas (P = .03 and .09), with similar results in pairwise comparisons of the corresponding thalamic ADC values (P = .02 and .06).

CONCLUSION

ADC analysis of a tumor's contrast-enhancing solid portion may aid preoperative molecular classification/prediction of pediatric medulloblastomas and may facilitate optimal surgical treatment planning, reducing surgery-induced morbidity.

Imaging features of medulloblastoma: Conventional imaging, diffusion-weighted imaging, perfusion-weighted imaging, and spectroscopy: From general features to subtypes and characteristics

Medulloblastoma is a frequent high-grade neoplasm among pediatric brain tumours. Its classical imaging features are a midline tumour growing into the fourth ventricle, hyperdense on CT-scan, displaying a hypersignal when using diffusion-weighted imaging, with a variable contrast enhancement. Nevertheless, atypical imaging features have been widely reported, varying according to the age of the patient, and histopathological subtype. In this study, we review the classical and atypical imaging features of medulloblastomas, with emphasis on advanced MRI techniques, histopathological and molecular subtypes and characteristics, and follow-up modalities.

MRI features as a helpful tool to predict the molecular subgroups of medulloblastoma: state of the art

Medulloblastoma is the most common malignant pediatric brain tumor. Medulloblastoma should not be viewed as a single disease, but as a heterogeneous mixture of various subgroups with distinct characteristics. Based on genomic profiles, four distinct molecular subgroups are identified: Wingless (WNT), Sonic Hedgehog (SHH), Group 3 and Group 4. Each of these subgroups are associated with specific genetic aberrations, typical age of onset as well as survival prognosis. Magnetic resonance imaging (MRI) is performed for all patients with brain tumors, and has a key role in the diagnosis, surgical guidance and follow up of patients with medulloblastoma. Several studies indicate MRI as a promising tool for early detection of medulloblastoma subgroups. The early identification of the subgroup can influence the extent of surgical resection, radiotherapy and chemotherapy targeted treatments. In this article, we review the state of the art in MRI-facilitated medulloblastoma subgrouping, with a summary of the main MRI features in medulloblastoma and a brief discussion on molecular characterization of medulloblastoma subgroups. The main focus of the article is MRI features that correlate with medulloblastoma subtypes, as well as features suggestive of molecular subgroups. Finally, we briefly discuss the latest trends in MRI studies and latest developments in molecular characterization.

Masses of developmental and genetic origin affecting the paediatric craniofacial skeleton

Although rare, masses and mass-like lesions of developmental and genetic origin may affect the paediatric craniofacial skeleton. They represent a major challenge in clinical practice because they can lead to functional impairment, facial deformation and disfigurement. The most common lesions include fibrous dysplasia, dermoid cysts, vascular malformations and plexiform neurofibromas. Less common lesions include torus mandibularis and torus palatinus, cherubism, nevoid basal cell carcinoma syndrome, meningoencephalocele and nasal sinus tract. This article provides a comprehensive approach for the evaluation of children with masses or mass-like lesions of developmental and genetic origin affecting the craniofacial skeleton. Typical findings are illustrated and the respective roles of computed tomography (CT), cone beam CT (CBCT), magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) sequences and ultrasonography (US) are discussed for the pre-therapeutic assessment, complex treatment planning and post-treatment surveillance. Key imaging findings and characteristic clinical manifestations are reviewed. Pitfalls of image interpretation are addressed and how to avoid them. TEACHING POINTS: • Masses of developmental and genetic origin may severely impair the craniofacial skeleton. • Although rare, these lesions have characteristic imaging features. • CT, MRI and ultrasonography play a key role in their work-up. • Recognition of pivotal imaging pearls and diagnostic pitfalls avoids interpretation errors.

Clinical, pathological, and molecular data on desmoplastic/nodular medulloblastoma: case studies and a review of the literature

The aim of this study was to better define the clinical and biopathological features of patients with desmoplastic/nodular medulloblastoma (DNMB) and to further characterize this subgroup. 17 children aged < 5 years, with initial DNMB treated according to the HIT-SKK protocol, were evaluated. A retrospective central radiological review, a pathological and immunohistochemical study, and array-CGH and sequencing of germline SUFU and PTCH1 genes were performed. 15 histologically reviewed cases were confirmed as DNMB including three cases of medulloblastoma with extensive nodularity. Median age at diagnosis was 26 months. Radiology showed five cases with a vermis location and one with T2 hyperintensity. All cases showed a SHH immunoprofile. A 9q deletion was found in 6 cases, a MYCN-MYCL amplification in 1 case, and a SUFU germline mutation in 1 case (/9). The presence of SUFU and PTCH1 germline mutations agreed with previous reports. At 3 years, progression-free survival and overallsurvival rates were 72 ± 15% and 85 ± 10%, respectively. The rate of recurrence was relatively high (4 patients). This may have been because chemotherapy was delayed in two cases. Age > 3 years, and residual tumor may also have been an explanation for recurrence.

In vivo Mn-enhanced MRI for early tumor detection and growth rate analysis in a mouse medulloblastoma model

Mouse models have increased our understanding of the pathogenesis of medulloblastoma (MB), the most common malignant pediatric brain tumor that often forms in the cerebellum. A major goal of ongoing research is to better understand the early stages of tumorigenesis and to establish the genetic and environmental changes that underlie MB initiation and growth. However, studies of MB progression in mouse models are difficult due to the heterogeneity of tumor onset times and growth patterns and the lack of clinical symptoms at early stages. Magnetic resonance imaging (MRI) is critical for noninvasive, longitudinal, three-dimensional (3D) brain tumor imaging in the clinic but is limited in resolution and sensitivity for imaging early MBs in mice. In this study, high-resolution (100 μm in 2 hours) and high-throughput (150 μm in 15 minutes) manganese-enhanced MRI (MEMRI) protocols were optimized for early detection and monitoring of MBs in a Patched-1 (Ptch1) conditional knockout (CKO) model. The high tissue contrast obtained with MEMRI revealed detailed cerebellar morphology and enabled detection of MBs over a wide range of stages including pretumoral lesions as early as 2 to 3 weeks postnatal with volumes close to 0.1 mm³. Furthermore, longitudinal MEMRI allowed noninvasive monitoring of tumors and demonstrated that lesions within and between individuals have different tumorigenic potentials. 3D volumetric studies allowed quantitative analysis of MB tumor morphology and growth rates in individual Ptch1-CKO mice. These results show that MEMRI provides a powerful method for early in vivo detection and longitudinal imaging of MB progression in the mouse brain.

A comparison of high b-value vs standard b-value diffusion-weighted magnetic resonance imaging at 3.0 T for medulloblastomas

OBJECTIVE

To investigate the utility of diffusion-weighted (DW) MRI using high b-value vs standard b-value for patients with medulloblastoma (MB). Minimum apparent diffusion coefficient (ADCMIN) values were also compared with tumour cellularity.

METHODS

High and standard b-value DW images were obtained for 17 patients with MB. The number and location of the lesions, signal intensities (SIs), signal-to-noise ratios (SNRs), contrast-to-noise ratios, contrast ratios (CRs) and ADCs of the lesions were compared. Tumour cellularity was also measured and compared with ADCMIN values.

RESULTS

All 20 lesions were hyperintense on the DW MR images with high and standard b-values. Four additional lesions were revealed on high b-value, and all 24 lesions were more conspicuous at high b-value. SI, SNR and ADC values for the lesions were lower in the high b-value images than in the standard b-value images. The ADCMIN value at b = 3000 s mm(-2) was more significantly associated with tumour cellularity than that at b = 1000 s mm(-2). CR values were significantly higher in the high b-value images than in the standard b-value images.

CONCLUSION

DW imaging using high b-value may be beneficial for detecting additional, less prominent lesions and may improve the contrast between MB lesions and normal tissue. A stronger inverse correlation with tumour cellularity was identified using the ADCMIN values at high b-value.

ADVANCES IN KNOWLEDGE

This study demonstrates the superiority of high b-value DW imaging compared with standard b-value imaging for the detection of MB lesions, especially those with subtle foci.

MRI T2 hypointensity of metastatic brain tumors from gastric and colonic cancers

BACKGROUND

Metastatic brain tumors from gastric and colon cancers are frequently revealed by hypointensity on T2-weighted magnetic resonance images (MRIs). However, the reason for this T2 hypointensity has yet to be clarified. We hypothesize that it is due to collagen deposition within the tissues.

METHODS

Seven metastatic brain tumors, from 3 gastric cancers and 4 colon cancers were investigated. The degree of hypointensity of these tumors in T2-weighted images was quantitatively assessed as the ratio of gray-scale densities of tumor to brain using ImageJ. The result was compared with the amount of collagen in the resected specimens, which was quantified by ImageJ analysis software, utilizing the colour deconvolution method following Azan-Mallory staining. The degree of hypointensity was also compared with the ratio of viable epithelial component area/whole tissue area. Additionally, collagen distribution was studied by immunohistochemical staining.

RESULTS

There was a clear negative correlation between intensity in T2-weighted images of these metastatic tumors and the amount of collagen they contained (R (2) = 0.766). However, there was no significant correlation between the T2 intensity and the ratio of viable epithelial component. Immunohistochemical analysis revealed that collagen types I, III, VII, X, and XI were expressed in the epithelial components and types IV, V, and VI were expressed in the stromal areas of the metastatic tumors. Collagen deposition was observed not only in stromal fibrous areas, but also in cytoplasmic areas in these metastatic tumors.

CONCLUSIONS

Hypointensity of metastatic brain tumors arising from gastric and colonic cancers may be due to the accumulation of collagen in the tissues.

Distinctive MRI features of pediatric medulloblastoma subtypes

OBJECTIVE

We hypothesized that the apparent diffusion coefficient (ADC) and other MRI features can be used to predict medulloblastoma histologic subtypes, as defined by the World Health Organization (WHO) in WHO Classification of Tumours of the Central Nervous System.

MATERIALS AND METHODS

A retrospective review of pediatric patients with medulloblastoma between 1989 and 2011 identified 38 patients with both pretreatment MRI and original pathology slides. The mean and minimum tumor ADC values and conventional MRI features were compared among medulloblastoma histologic subtypes.

RESULTS

The cohort of 38 patients included the following histologic subtypes: 24 classic medulloblastomas, nine large cell (LC) or anaplastic medulloblastomas, four desmoplastic medulloblastomas, and one medulloblastoma with extensive nodularity. The median age at diagnosis was 8 years (range, 1-21 years) and the median follow-up time was 33 months (range, 0-150 months). The mean ADC (× 10(-3) mm(2)/s) was lower in classic medulloblastoma (0.733 ± 0.046 [SD]) than in LC or anaplastic medulloblastoma (0.935 ± 0.127) (Mann-Whitney test, p = 0.004). Similarly, the minimum ADC was lower in classic medulloblastoma (average ± SD, 0.464 ± 0.056) than in LC or anaplastic medulloblastoma (0.630 ± 0.053) (p = 0.004). The MRI finding of focal cysts correlated with the classic and desmoplastic subtypes (Fisher exact test, p = 0.026). Leptomeningeal enhancement positively correlated with the LC or anaplastic medulloblastoma subtype and inversely correlated with the classic medulloblastoma and desmoplastic medulloblastoma subtypes (p = 0.04). Ring enhancement correlated with tumor necrosis (p = 0.022) and with the LC or anaplastic medulloblastoma histologic subtype (p < 0.001).

CONCLUSION

The LC or anaplastic medulloblastoma subtype was associated with increased ADC and with ring enhancement, the latter of which correlated with tumor necrosis. These features could be considered in the evaluation of high-risk medulloblastoma subtypes.