Research Presentation Session

RPS 916 - Brain, head and neck tumours: advanced imaging and radiomics

Lectures

1
RPS 916 - 18F-FET or 18F-FCH PET/CT in the primary diagnosis of low-grade glioma: a pilot study

RPS 916 - 18F-FET or 18F-FCH PET/CT in the primary diagnosis of low-grade glioma: a pilot study

05:33M. Hodolic, Graz Seisberg / AT

Purpose:

Gliomas are associated with varied survival, in part linked with their histological subtype. The diagnosis of low-grade glioma (LGG) is challenging, as conventional imaging modalities can often give inconclusive or equivocal results. Function imaging modalities can provide additional metabolic information. O- (2-[18F]-fluoroethyl) -L-tyrosine (18F-FET) is radiopharmaceutical approved for the characterisation of glioma-suggestive brain lesions. 18F-FET displays a high tumour-to-background ratio and no accumulation in inflammatory lesions. Because of low uptake in normal brain parenchyma, some centres use fluoromethyl-(18F)-dimethyl-2-hydroxyethyl-ammonium chloride (18F-FCH) PET for the characterisation of glioma-suggestive brain lesions.

The aim of this study was to determine the diagnostic accuracy of 18F-FET and 18F-FCH PET/CT in patients with primary LGG.

Methods and materials:

11 patients aged 21-80 years with MRI-suspected LGG were involved. Patients underwent 18F-FET and 18F-FCH PET/CT within one week. Surgery and pathohistological diagnoses were performed in the next two weeks.

Results:

11/11 patients with suspected LGG underwent MRI, 18F-FET and 18F-FCH PET/CT. 9/11 patients underwent surgery and pathohistological diagnosis.

6 patients positive on 18F-FET (SUVmax values ranging from 1.3-3.1) and negative on 18F-FCH PET had a pathohistological diagnosis of LGG (2 ganglioma and 4 diffuse astrocytomas).

2 patients with 18F-FET and 18F-FCH PET avid lesion had a final diagnosis of glioblastoma multiforme.

1 patient negative on 18F-FET and negative on 18F-FCH PET had a diagnosis of focal cortical dysplasia.

2/11 patients are still waiting for surgery.

Conclusion:

Appropriate radiopharmaceutical should be chosen before performing PET/CT in patients with newly diagnosed LGG. 18F-FET seems to be more accurate than 18F-FCH in the primary diagnosis of LGG.

Limitations:

The small number of patients.

Ethics committee approval

The University Hospital Centre Zagreb, Croatia, approved this study.

Funding:

18F-FET was received for free.

2
RPS 916 - T2-FLAIR mismatch in grade II and III gliomas: fifty shades of mismatch?

RPS 916 - T2-FLAIR mismatch in grade II and III gliomas: fifty shades of mismatch?

05:39A. Desagneaux, La Tronche / FR

Purpose:

The identification of imaging criteria predictive of a specific molecular subtype has become a priority to enable accurate glioma subtypes diagnosis with imaging. We aimed to assess possible variants of the typical T2-FLAIR mismatch in grade II and III glioma tumours with correlation to both histologic and molecular findings.

Methods and materials:

A single-centre retrospective study including WHO grade II and III gliomas with complete IDH and 1p19q status was conducted. Two types of mismatch were defined. Typical, as previously described, and atypical T2-FLAIR mismatch, defined as the presence of one or more of the following characteristics: very low signal in flair, thick T2-FLAIR rim hyperintensity, irregular shaped T2-FLAIR mismatch, incomplete rim, or peri T2-FLAIR mismatch tumoural spread.

Results:

Among 39 included patients, 20 had IDH–mutant astrocytomas, 14 had IDH–mutant oligodendromas, and 5 had IDH-wild type. The T2-FLAIR mismatch was found in 16/20 astrocytoma IDH-mutant cases (80%), with an excellent inter-reader agreement (k of 0.89 (95% CI 0.76-1.01, p<0.001) and high PPV (100%), specificity 100%, NPV 82.6%, and sensibility 80%). The T2-FLAIR mismatch sign among IDH–mutant astrocytoma was present with a typical presentation in 6/20 (30%) cases and atypical presentation was present in 10/20 (50%) cases.

Conclusion:

This study confirmed the usefulness of the T2-FLAIR mismatch to help to diagnose IDH-mutant astrocytoma. Atypical T2-FLAIR mismatch should also be considered, as this study has shown that broadening the definition of the already well-described T2-FLAIR mismatch may improve the MRI prediction accuracy of molecular subtypes in grade II and III gliomas.

Limitations:

A retrospective study with a small sample.

Ethics committee approval

Study ethics approval (CECIC Rhône-Alpes-Auvergne, Clermont-Ferrand, IRB 5891).

Funding:

No funding was received for this work.

3
RPS 916 - Early post-treatment assessment of multi-parametric MRI after stereotactic radiosurgery: can it predict the long-term response of brain metastases?

RPS 916 - Early post-treatment assessment of multi-parametric MRI after stereotactic radiosurgery: can it predict the long-term response of brain metastases?

04:31P. Arcuri, Lamezia Terme / IT

Purpose:

Imaging criteria to evaluate the response of brain metastases to stereotactic radiosurgery (SRS) in the early post-treatment period remains an important need not yet resolved. The aim of this study is to correlate early (within 12 weeks) post-treatment multi-parametric MRI changes with long-term outcomes after treatment of brain metastases with SRS.

Methods and materials:

We evaluated 24 patients with multi-parametric MRI techniques, including spectroscopy, diffusion, and perfusion imaging in the pre-and post-treatment early period for the differentiation of radiation-related changes and tumour recurrence after SRS in intracranial metastases. Patients were followed longitudinally until death, progression, or intervention. All patients presented with enlargement of the treated lesion, an increase in perilesional brain oedema, and aggravation of neurological signs and symptoms from 7-29 weeks after primary treatment. Kruskal–Wallis' non-parametric test was performed. Sensitivity, specificity, and accuracy were assessed. Fisher’s exact test was used to evaluate statistical significance. Histology or radiological follow-up was the gold standard.

Results:

A low apparent diffusion coefficient (ADC) <1×10-3 mm2/s, a high relative cerebral blood volume (rCBV) ratio >2.3, and a high choline/creatine (Cho/Cr) ratio >1.9 suggested tumour recurrence. A high ADC >1×10-3 mm2/s, a low rCBV ratio <2.3, and a Cho/Cr ratio <1.9 suggested SRS-induced radiation changes. Sensitivity, specificity, and diagnostic accuracy were, respectively: rCBV=82%, 79%, and 81%, ADC= 75%, 73%, and 79%, and Cho/Cr ratio=76%, 80%, and 82%.

Conclusion:

Early post-treatment rCBV and, to a lesser extent, ADC values and Cho/Cr ratios may be used as imaging biomarkers to help predict the long-term response of brain metastases to SRS. This can help identify patients who will ultimately fail SRS and allow for timelier adjustments in the treatment approach.

Limitations:

The different primitive neoplasms.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

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