Context[18F]FDG PET/CT improves adrenal tumour characterization. However, there is still no consensus regarding the optimal imaging biomarkers of malignancy.ObjectivesTo assess the performance of Tumour standardized uptake value (SUV)max:Liver SUVmax for malignancy‐risk and to build and evaluate a prediction model.Design/MethodsThe cohort consisted of consecutive patients with adrenal masses evaluated by [18F]FDG PET/CT. The gold standard for malignancy was based on histology or a multidisciplinary consensus in nonoperated cases. The performance of the previously reported cut‐off for Tumour SUVmax:Liver SUVmax (>1.5) was evaluated in this independent cohort. Additionally, a predictive model of malignancy was built from the training cohort (previous study) and evaluated in the validation cohort (current study).ResultsSixty‐four patients were evaluated; 28% of them had a Cushing's syndrome. Fifty‐four adrenal masses were classified as benign and 10 as malignant (including 7 adrenocortical carcinomas). Compared to benign masses, malignant lesions were larger in size, had higher unenhanced densities and higher [18F]FDG uptake. CT‐derived anthropometric parameters did not differ between benign and malignant masses. A tumour SUVmax:Liver SUVmax > 1.5 showed a good diagnostic performance: Se = 90.0%/Sp = 92.6%/PPV = 69.2%/NPV = 98.0% and accuracy = 92.2%. A predictive model based on tumour size and tumour‐to‐liver uptake SUVmax ratio for malignancy‐risk was validated and provides a complementary approach to the ratio.ConclusionsTumour SUVmax:Liver SUVmax uptake ratio is a useful biomarker for diagnosis of adrenal masses. Another tactic would be to calculate with the model an individual risk of malignancy and integrate this information into a shared decision‐making process.

Somatostatin receptor (SSTR)-targeted peptide receptor radionuclide therapy (PRRT) represents a promising approach for treatment-refractory meningiomas progressing after surgery and radiotherapy. The aim of this study was to provide outcomes of patients harboring refractory meningiomas treated by 177Lu-DOTATATE and an overall analysis of progression-free survival at 6 months (PFS-6) of the same relevant studies in the literature. Eight patients with recurrent and progressive WHO grade II meningiomas were treated after multimodal pretreatment with 177Lu-DOTATATE between 2019 and 2022. Primary and secondarily endpoints were progression-free survival at 6-months (PFS-6) and toxicity, respectively. PFS-6 analysis of our case series was compared with other similar relevant studies that included 86 patients treated with either 177Lu-DOTATATE or 90Y-DOTATOC. Our retrospective study showed a PFS-6 of 85.7% for WHO grade II progressive refractory meningiomas. Treatment was clinically and biologically well tolerated. The overall analysis of the previous relevant studies showed a PFS-6 of 89.7% for WHO grade I meningiomas (n = 29); 57.1% for WHO grade II (n = 21); and 0 % for WHO grade III (n = 12). For all grades (n = 86), including unknown grades, PFS-6 was 58.1%. SSTR-targeted PRRT allowed us to achieve prolonged PFS-6 in patients with WHO grade I and II progressive refractory meningiomas, except the most aggressive WHO grade II tumors. Large scale randomized trials are warranted for the better integration of PRRT in the treatment of refractory meningioma into clinical practice guidelines.

Therapies for metastatic SDHB-dependent pheochromocytoma and paraganglioma (PPGL) are limited and poorly efficient. New targeted therapies and identification of early non-invasive biomarkers of response are thus urgently needed for these patients. We characterized an in vivo allograft model of spontaneously immortalized murine chromaffin cells (imCC) with inactivation of the Sdhb gene by dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) and 18FDG-PET. We evaluated the response to several therapies: IACS-010759 (mitochondrial respiratory chain complex I inhibitor), sunitinib (tyrosine kinase inhibitor with anti-angiogenic activity), talazoparib (PARP inhibitor) combined or not to temozolomide (alkylating agent), pharmacological inhibitors of HIF2α (PT2385 and PT2977 (belzutifan)) and molecular inactivation of HIF2α (imCC Sdhb-/- shHIF2α). Multimodal imaging was performed, including magnetic resonance spectroscopy (1H-MRS) to monitor the level of succinate in vivo. The allografted model of Sdhb-/- imCC reflected SDHB-deficient tumors, with increased angiogenesis and a particular avidity for 18FDG. After 14 days of treatment, IACS-010759, sunitinib and talazoparib at high doses allowed a significant reduction of the tumor volumes. In contrast to the tumor growth inhibition observed in Sdhb-/- shHIF2α imCC tumors, pharmacological inhibitors of HIF2α (PT2385 and belzutifan) showed no anti-tumor action in this model, alone or in combination with sunitinib. 1H-MRS, but not DCE-MRI, enabled monitoring response to sunitinib, which was the best treatment in this study, promoting a decrease in succinate levels detected in vivo. This study paves the way for new therapeutic options and reveals a potential new early biomarker of response to treatment in SDHB-dependent PPGL.