Detecting non-germinomatous germ cell tumor component by arterial spin labeling perfusion-weighted MR imaging in central nervous system germ cell tumor

Update on MRI in pediatric intracranial germ cell tumors-The clinical and radiological features

Intracranial germ cell tumors (iGCTs) are uncommon brain tumors that mainly occur in children. Differing in histology, location, and gender of the patients, iGCTs are often divided into germinomas and non-germinomatous germ cell tumors (NGGCTs). Early diagnosis and timely treatment are crucial to iGCTs, the subtypes of which have substantial variations. This review summarized the clinical and radiological features of iGCTs at different sites, and reviewed the recent advances in neuroimaging of iGCTs, which can help predict tumor subtypes early and guide clinical decision-making.

Multiparametric Framework Magnetic Resonance Imaging Assessment of Subtypes of Intracranial Germ Cell Tumors Using Susceptibility Weighted Imaging, Diffusion-Weighted Imaging, and Dynamic Susceptibility-Contrast Perfusion-Weighted Imaging Combined With Conventional Magnetic Resonance Imaging

BACKGROUND

Intracranial germ cell tumors (iGCTs) are classified into two pathological subtypes (germinomas [GEs] and nongerminomatous germ cell tumors [NGGCTs]), with distinct treatment strategy and prognosis. Accurate preoperative determination of iGCT subtypes is essential to guide clinical decision-making and prognosis assessment.

PURPOSE

To investigate the diagnostic value of diffusion-weighted imaging (DWI), susceptibility weighted imaging (SWI), and dynamic susceptibility-contrast perfusion-weighted imaging (DSC-PWI) combined with conventional magnetic resonance imaging (cMRI) in finding subtypes of iGCTs.

STUDY TYPE

Retrospective.

POPULATION

A total of 40 patients (45% male and 55% female) with iGCTs.

FIELD STRENGTH/SEQUENCE

A 3 T; <T1WI, T2WI, T1WI + C, DWI, SWI, DSC-PWI>.

ASSESSMENT

The parameters of DWI and DSC-PWI were calculated based on extracted parameters of multiparametric MRIs. The characteristics of SWI and cMRI were also compared in GEs and NGGCTs.

STATISTICAL TESTS

The diagnostic efficacy of the minimum apparent diffusion coefficient (ADCmin), time-to-peak (TTP), relative mean transit time (rMTT), relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV) maps, and cMRI features in iGCT classification was evaluated by receiver operating characteristic curve (ROC) analyses. We calculated the sensitivity, specificity, AUC, and Youden index of the hybrid MR evaluation methods. A prospective cohort (five GEs and five NGGCTs) was designed as a simulation set to test the model. The significance threshold was set at P < 0.01.

RESULTS

The ADCmin (1039.100 ± 453.830 vs. 1400.050 ± 394.650), rCBF values (20.650 ± 6.260 vs. 51.170 ± 6.570), and TTP values (24.450 ± 3.160 vs. 28.950 ± 5.120) were significantly lower in GEs than in NGGCTs. The combination of ADCmin, DSC-PWI, and cMRI showed the heights AUC (AUC = 0.962). The iGCT multiparametric framework showed the AUC was 0.958 in the simulation set.

DATA CONCLUSION

The iCGT multiparametric framework might be an effective diagnostic approach of iGCT subtype. The application of cMRI (T1WI, T2WI, and Gd-T1WI) with advanced imaging modalities (DWI, SWI, and PWI) had the best performance for classifying iGCT subtypes.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Molecular Pathology and Targeted Therapies for Personalized Management of Central Nervous System Germinoma

Intracranial germinomas are rare tumours, usually affecting male paediatric patients. They frequently develop in the pineal and suprasellar regions, causing endocrinological disturbances, visual deficits, and increased intracranial pressure. The diagnosis is established on magnetic resonance imaging (MRI), serum and cerebrospinal fluid (CSF) markers, and tumour stereotactic biopsy. Imaging techniques, such as susceptibility-weighted imaging (SWI), T2* (T2-star) gradient echo (GRE) or arterial spin labelling based perfusion-weighted MRI (ASL-PWI) facilitate the diagnosis. Germinomas are highly radiosensitive tumours, with survival rates >90% in the context of chemoradiotherapy. However, patients with resistant disease have limited therapeutic options and poor survival. The aim of this review is to highlight the genetic, epigenetic, and immunologic features, which could provide the basis for targeted therapy. Intracranial germinomas present genetic and epigenetic alterations (chromosomal aberrations, KIT, MAPK and PI3K pathways mutations, DNA hypomethylation, miRNA dysregulation) that may represent targets for therapy. Tyrosine kinase and mTOR inhibitors warrant further investigation in these cases. Immune markers, PD-1 (programmed cell death protein 1) and PD-L1 (programmed death-ligand 1), are expressed in germinomas, representing potential targets for immune checkpoint inhibitors. Resistant cases should benefit from a personalized management: genetic and immunological testing and enrolment in trials evaluating targeted therapies in intracranial germinomas.