FDG avid cerebellar atypical meningioma masquerading as solitary brain metastases in a recently diagnosed breast malignancy: a toss between MR and CT

Background SUV Max is a glycolytic index obtained from PET imaging, relates to tumour cell proliferation. FDG uptake (i.e. SUV max) is found to be high in aggressive tumours and is used to identify malignant from benign pathologies. Meningiomas are intracranial tumours which display varying grades of FDG avidity based on its biological aggressiveness. Benign grade I meningiomas are FDG non-avid, while the rest of the typical and atypical meningiomas show varying degrees of FDG avidity. Uptake of FDG can be high in certain infectious and inflammatory brain etiologies and pose a diagnostic challenge in differentiating benign brain lesions from neoplasms. MRI is the preferred modality for accurately identifying meningiomas, providing superior contrast differentiation and its ability to differentiate extra-axial from intra-axial brain lesions. CT is said to be superior in specific types of meningioma where there is calcification and adjacent changes in calvarium. Although typical meningiomas have characteristic MRI features, care must be taken to avoid misleading diagnosis between brain tumours and atypical meningiomas. Case presentation We are presenting a recently diagnosed case of invasive breast carcinoma (Ca) referred for staging by PET/MR imaging. Based on atypical DWI and ADC map findings, MRI falsely reported an atypical meningioma as a brain metastasis. Abnormal intense FDG uptake was noted in a well-defined homogeneously enhancing mass lesion in posterior fossa in left paramedian aspect and broad base to left transverse sinus protruding into left cerebellar hemisphere. Atypical meningioma Grade III, i.e. papillary meningioma was later histologically proven. Conclusions We wish to highlight the inconsistency of DWI and ADC map MR findings in papillary meningioma masquerading as solitary brain metastases in a Ca breast patient on 18F FDG PET/MR imaging. From an imaging standpoint, it is important to recognize the variable and pleomorphic features exhibited by meningiomas in MR based on atypical location, histological subtypes, and biologic behaviours. Further FDG PET was incremental in displaying a high SUV max indicating biologic aggressiveness of lesion and correlating with the CT diagnosis of papillary meningioma.

RADT-31. TREATMENT TRENDS AND SURVIVAL OUTCOMES IN ATYPICAL MENINGIOMA

BACKGROUND WHO grade II (atypical) meningiomas are treated with surgical resection, often followed by adjuvant fractionated radiation therapy (FRT). The increased availability of frameless stereotactic radiosurgery (SRS) presents an opportunity to offer patients a high biological effective dose over fewer fractions. Here we study the patterns of care and outcomes of these two forms of adjuvant RT. METHODS Patients with atypical meningioma were abstracted from the National Cancer Database (NCDB). Descriptive statistics were reported, and differences between treatment groups were assessed using either a chi-square test or ANOVA. Patients were grouped by treatment type and Kaplan Meier (KM) analysis was performed to compare overall survival (OS) using a log rank test. Univariable (UVA) and multivariable (MVA) cox regression analyses were completed. RESULTS Of 10,015 cases diagnosed from 2004-2016, 7,153 received surgery alone, 2,059 received surgery and adjuvant FRT (S+RT), and 362 received adjuvant SRS (S+SRS). The use of adjuvant RT increased by 71.8% for S+RT and 97.8% for S+SRS. In 2004, 15.1% of 443 registered patients received S+RT and 2.26% received S+SRS, while in 2016 these figures were 26.0% and 4.47%, respectively, for the 1051 registered patients (p< 0.001 and 0.022, respectively). For the 8,636 patients with survival data there was no significant difference in median OS between S+RT and S+SRS (130 months vs. 125 months, log rank p=0.935). On UVA, S+RT conferred better survival compared to surgery alone (HR 0.81 [0.72-0.91], p< 0.001) while S+SRS trended towards better survival (HR 0.82 [0.64-1.06], p=0.124). On MVA, no significant OS benefit was seen with S+RT (HR 0.96 [0.85-1.08], p=0.491) or S+SRS (HR 0.90 [0.69-1.16], p=0.413) versus surgery alone. CONCLUSIONS While the use of adjuvant RT for atypical meningioma has increased substantially since 2004, OS is comparable between FRT and SRS. The data presented here support further prospective investigation of adjuvant SRS.

Adjuvant radiotherapy in a case of atypical meningioma after gross total resection: an unresolved issue

We present a case of a 48-year-old man diagnosed with parasagittal atypical meningioma (AM) involving biparietal bones with intracranial and extracranial extension up to galea aponeurotica of the scalp. The patient underwent Simpson’s grade 2 resection (GTR (gross total tumour resection) with coagulation of dural attachment). Currently, in AMs, the role of adjuvant radiotherapy is controversial after GTR. Here, through this case, we have discussed in detail issues related to tumour origin, that is, primary versus secondary extradural meningioma and controversial topics regarding the role of adjuvant radiotherapy in the management of AMs. We have presented our radiation treatment strategy addressing the high-risk zones related to tumour extension in this case.

Combining FORGE Score and Histopathological Diagnostic Criteria of Atypical Meningioma Enables Risk Stratification of Tumor Progression

More than 50% of atypical meningiomas regrow within 5 years after surgery. FORGE score is a newly created tool to estimate the MIB-1 index in cranial meningiomas. In this investigation, we aimed to assess the predictive value of the FORGE score in combination with major diagnostic criteria of atypical meningioma (brain invasion, mitotic count ≥ 4) regarding recurrence in atypical meningiomas. We included patients operated on primary atypical meningiomas in our center from 2011 to 2019. The study included 71 patients (58% women, median age 63 years). ROC curves revealed a superiority of FORGE score combined with histopathological diagnostic criteria of atypical meningioma (AT-FORGE) in the prediction of tumor progression compared to FORGE score only (AUC: 0.72; 95% CI: 0.54–0.91, cut-off: ≥5/<5, sensitivity: 75%, specificity: 78%). Patients with an AT-FORGE score ≥ 5 had a shorter time to tumor progression (32.8 vs. 71.4 months, p < 0.001) in the univariable analysis. Multivariable cox regression analysis revealed significant predictive value of Simpson grade > II, presence of multiple meningiomas and AT-FORGE score ≥ 5 for tumor progression. The combination of histopathological diagnostic criteria for atypical meningioma with FORGE score might facilitate an effective identification of patients with an atypical meningioma who have an increased risk of tumor progression.