Evaluation of the Impact of Magnetic Resonance Imaging with Susceptibility-weighted Imaging for Screening and Surveillance of Radiation-induced Cavernomas in Long-term Survivors of Malignancy

AIMS

Radiation-induced cavernomas (RIC) are common late toxicities in long-term survivors of malignancy following cerebral irradiation. However, the natural history of RIC is poorly described. We report the first series of long-term surveillance of RIC using modern magnetic resonance imaging (MRI) including highly sensitive susceptibility-weighted imaging (SWI). The aims of this research were to better characterise the natural history of RIC and investigate the utility of MRI-SWI for screening and surveillance.

MATERIALS AND METHODS

Eligibility required long-term survivors of malignancy with previous exposure to cerebral irradiation and RIC identified on MRI-SWI surveillance. The number and size of RIC were reported on Baseline MRI-SWI and last Follow-up MRI-SWI.

RESULTS

In total, 113 long-term survivors with RIC underwent MRI-SWI surveillance; 109 (96%) were asymptomatic at the time of RIC diagnosis. The median age at cerebral irradiation was 9.3 years; the median radiotherapy dose was 50.4 Gy. The median time from cerebral irradiation to Baseline MRI-SWI was 17.9 years. On Baseline MRI-SWI, RIC multiplicity was present in 89% of patients; 34% had >10 RIC; 65% had RIC ≥4 mm. The median follow-up from Baseline MRI-SWI was 7.3 years. On Follow-up MRI-SWI, 96% of patients had multiple RIC; 62% had >10 RIC; 72% had RIC ≥4 mm. Of the 109 asymptomatic patients at RIC diagnosis, 96% remained free from RIC-related symptoms at 10 years. Only two required neurosurgical intervention for RIC; there was no RIC-related mortality.

CONCLUSIONS

RIC are commonly multiple, asymptomatic and typically increase in size and number over time. Our findings suggest that MRI-SWI for screening of RIC is unlikely to influence longer term intervention in asymptomatic cancer survivors. In the absence of neurological symptoms, assessment or monitoring of RIC are insufficient indications for MRI-SWI surveillance for long-term survivors of malignancy with past exposure to cerebral irradiation.

The imaging of immunotherapy-related hypophysitis and other pituitary lesions in oncology patients

Immunotherapy has revolutionised the treatment of metastatic disease from a variety of different primaries, but is frequently associated with immune-related adverse events. This review illustrates the imaging features of immunotherapy-related hypophysitis (IH) and some of the important differential diagnoses in oncology patients. The key radiological characteristic of IH is diffuse, modest enlargement of the pituitary gland with temporal evolution attributable to immunotherapy. Pituitary enlargement is transient, and the gland size returns to baseline size or smaller within months. IH is usually associated with homogeneous enhancement of the pituitary gland, and the pituitary stalk may be thickened. Larger pituitary size, deviation of the pituitary stalk, the presence of a discrete lesion surrounding by normal pituitary tissue, sellar expansion, and clival invasion are not typical of IH and suggest alternate diagnoses. On integrated 2-[¹⁸F]-fluoro-2-deoxy-d-glucose positron-emission tomography (PET)/computed tomography (CT), a transient increase in the metabolic activity of the pituitary gland with subsequent decline to background activity is also suggestive of IH. We suggest that the sella is assessed routinely on imaging performed in the first 6 months after commencing immunotherapy to detect subtle changes. Radiologists should also be aware of features that either support a diagnosis of IH or suggest alternate diagnoses.

Noninvasive Determination of IDH and 1p19q Status of Lower-grade Gliomas Using MRI Radiomics: A Systematic Review

BACKGROUND

Determination of isocitrate dehydrogenase (IDH) status and, if IDH-mutant, assessing 1p19q codeletion are an important component of diagnosis of World Health Organization grades II/III or lower-grade gliomas. This has led to research into noninvasively correlating imaging features ("radiomics") with genetic status.

PURPOSE

Our aim was to perform a diagnostic test accuracy systematic review for classifying IDH and 1p19q status using MR imaging radiomics, to provide future directions for integration into clinical radiology.

DATA SOURCES

Ovid (MEDLINE), Scopus, and the Web of Science were searched in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Diagnostic Test Accuracy guidelines.

STUDY SELECTION

Fourteen journal articles were selected that included 1655 lower-grade gliomas classified by their IDH and/or 1p19q status from MR imaging radiomic features.

DATA ANALYSIS

For each article, the classification of IDH and/or 1p19q status using MR imaging radiomics was evaluated using the area under curve or descriptive statistics. Quality assessment was performed with the Quality Assessment of Diagnostic Accuracy Studies 2 tool and the radiomics quality score.

DATA SYNTHESIS

The best classifier of IDH status was with conventional radiomics in combination with convolutional neural network-derived features (area under the curve  = 0.95, 94.4% sensitivity, 86.7% specificity). Optimal classification of 1p19q status occurred with texture-based radiomics (area under the curve  = 0.96, 90% sensitivity, 89% specificity).

LIMITATIONS

A meta-analysis showed high heterogeneity due to the uniqueness of radiomic pipelines.

CONCLUSIONS

Radiogenomics is a potential alternative to standard invasive biopsy techniques for determination of IDH and 1p19q status in lower-grade gliomas but requires translational research for clinical uptake.

Neuro-Oncology and Radiogenomics: Time to Integrate?

Radiogenomics aims to predict genetic markers based on imaging features. The critical importance of molecular markers in the diagnosis and management of intracranial gliomas has led to a rapid growth in radiogenomics research, with progressively increasing complexity. Despite the advances in the techniques being examined, there has been little translation into the clinical domain. This has resulted in a growing disconnect between cutting-edge research and assimilation into clinical practice, though the fundamental goal is for these techniques to improve patient care. The goal of this review, therefore, is to discuss possible clinical scenarios in which the addition of radiogenomics may aid patient management. This includes facilitating patient counseling, determining optimal patient management when complete molecular characterization is not possible, reclassifying tumors, and overcoming some of the limitations of histologic assessment. The review also discusses considerations for selecting relevant radiogenomic features based on the clinical setting.

Non-Contrast-Enhancing Tumor: A New Frontier in Glioblastoma Research

There is a growing understanding of the prognostic importance of non-contrast-enhancing tumor in glioblastoma, and recent attempts at more aggressive management of this component using neurosurgical resection and radiosurgery have been shown to prolong survival. Optimizing these therapeutic strategies requires an understanding of the features that can distinguish non-contrast-enhancing tumor from other processes, in particular vasogenic edema; however, the limited and heterogeneous manner in which it has been defined in the literature limits clinical translation. This review covers pertinent literature on our growing understanding of non-contrast-enhancing tumor and focuses on key conventional MR imaging features for improving its delineation. Such features include subtle differences in the degree of FLAIR hyperintensity, gray matter involvement, and focal mass effect. Improved delineation of tumor from edema will facilitate more aggressive management of this component and potentially realize associated survival benefits.

MRI Features Can Predict 1p/19q Status in Intracranial Gliomas

BACKGROUND AND PURPOSE

The 2016 revision of the World Health Organization Classification of Tumors of the Central Nervous System mandates codeletion of chromosomes 1p and 19q for the diagnosis of oligodendroglioma. We studied whether conventional MR imaging features could predict 1p/19q status.

MATERIALS AND METHODS

Patients with previous 1p/19q testing were identified through pathology department records, typically performed on the basis of an oligodendroglial component on routine histology; 69 patients met the inclusion criteria. Preoperative imaging of patients with grade II or III gliomas was retrospectively assessed by 2 neuroradiologists, blinded to the 1p/19q status. Thirteen MR imaging features were first assessed in a small initial cohort (n = 10), after which the criteria were narrowed for the remaining patients as a validation cohort.

RESULTS

There was 85% agreement between radiologists for the overall prediction of 1p/19q status in the validation cohort, with an accuracy of 84%. The presence of >50% T2-FLAIR mismatch and calcification was found to be the most useful for predicting 1p/19q status. The >50% T2-FLAIR mismatch variable was demonstrated in 14 tumors and had 100% specificity for identifying a noncodeleted tumor (P = .001), with 97% interobserver correlation. Calcification was visualized in 7 tumors, 6 of which were 1p/19q codeleted (specificity, 97%; P = .006), with 100% interobserver correlation.

CONCLUSIONS

The presence of >50% T2-FLAIR mismatch is highly predictive of a noncodeleted tumor, while calcifications suggest a 1p/19q codeleted tumor. If formal 1p/19q testing is not possible, a combined MR imaging-histologic assessment may improve the diagnostic accuracy over histology alone.

Intracranial involvement by multiple myeloma

Intracranial involvement is a rare complication of multiple myeloma. It results either from direct extra-osseous spread from adjacent skeletal plasmacytomas or extra-medullary disease via haematogenous dissemination. The imaging appearances are non-specific, and dural, leptomeningeal, and parenchymal involvement can all occur. The purpose of this review is to illustrate the various neuroimaging appearances of this rare entity, focusing on MRI.

MRI grading versus histology: predicting survival of World Health Organization grade II-IV astrocytomas

BACKGROUND AND PURPOSE

Histologic grading of intracranial astrocytomas is affected by sampling error and substantial inter- and intraobserver variability. We proposed that incorporating MR imaging into grading will predict patient survival more accurately than histopathology alone.

MATERIALS AND METHODS

Patients with a new diagnosis of World Health Organization grades II-IV astrocytoma or mixed oligoastrocytoma diagnosed between September 2007 and December 2010 were identified. Two hundred forty-five patients met the inclusion criteria. Preoperative MRIs were independently reviewed by 2 readers blinded to the histologic grade, and an MR imaging grade was given. The MR imaging and histopathologic grades were compared with patient survival.

RESULTS

Patients with grade II or III astrocytomas on histology but evidence of necrosis on MR imaging (consistent with a grade IV tumor) had significantly worse survival than patients with the same histology but no evidence of necrosis on MR imaging (P = .002 for grade II histology and P = .029 for grade III). Their survival was not significantly different from that in patients with grade IV tumors on histology (P = .164 and P = .385, respectively); this outcome suggests that all or most are likely to have truly been grade IV tumors. MR imaging evidence of necrosis was less frequent in grade II and III oligoastrocytomas, preventing adequate subgroup analysis.

CONCLUSIONS

MR imaging can improve grading of intracranial astrocytomas by identifying patients suspected of being undergraded by histology, with high interobserver agreement. This finding has the potential to optimize patient management, for example, by encouraging more aggressive treatment earlier in the patient's course.