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Introduction: Pheochromocytomas and paragangliomas (PPGLs) typically secrete catecholamines and their metabolites (metanephrines [MN] and normetanephrine [NMN]). Catecholamines are synthesized by several enzymes: phenylalanine hydroxylase (encoded by PAH), tyrosine hydroxylase (TH), aromatic L‐amino acid decarboxylase (DDC), dopamine β‐hydroxylase (DBH), and phenylethanolamine N‐methyltransferase (PNMT). MN/NMN secretion varies between anatomical and molecular subgroups. The aim of this study was to assess the correlation between DNA methylation of catecholamine synthesis genes and MN/NMN secretion. Methods: Gene promoter methylation of PAH, TH, AADC, DBH, and PNMT were extracted and calculated based on publicly available data. Comparisons and correlation analysis were performed between MN ± NMN (MN/NMN), NMN only, and neither/unknown secretion patterns. Methylation levels and MN/NMN patterns were compared by three genetic alteration subgroups: pseudohypoxia (PH), kinase signaling (KS), and others. Results: A total of 178 cases were included. Methylation of PAH CpGs negatively correlated with probability for MN/NMN secretion (p <.05 for all CpGs) and positively with NMN‐only secretion. NMN‐only secreting tumors had significantly higher promoter methylation of PAH, DBH, and PNMT compared with MN/NMN‐secreting tumors. MN/NMN‐secreting PPGLs had mainly KS alterations (52.1%), whereas NMN‐only PPGLs had PH alterations (41.9%). PPGLs in the PH versus KS group had gene promoter hypermethylation of PAH (p =.002), DBH (p =.02), and PNMT (p =.003). Conclusions: Promoter methylation of genes encoding catecholamine synthesis enzymes is strongly and inversely correlated with MN/NMN patterns in PPGLs. KS and PH‐related tumors have distinct methylation patterns. These results imply that methylation is a key regulatory mechanism of catecholamine synthesis in PPGLs. This study aimed to assess a possible association between the genetic background of pheochromocytoma/paraganglioma (PPGL) and gene regulation of catecholamine synthesis enzymes. We found that kinase signaling‐related and pseudohypoxia‐related alterations have distinct methylation patterns, implying methylation as a key regulatory mechanism of catecholamine synthesis in PPGLs. [ABSTRACT FROM AUTHOR]

PURPOSE: Patients with advanced, well-differentiated neuroendocrine tumors (WD-NETs) often require both peptide receptor radionuclide therapy (PRRT) and subsequent chemotherapy. However, no mid-PRRT predictors are available to identify patients who will not benefit from subsequent PRRT to limit their radiation exposure. Our aim is to characterize patients for whom subsequent PRRT is less efficacious on the basis of mid-PRRT evaluation. MATERIALS AND METHODS: A retrospective study of patients with WD-NET who underwent ≥four PRRT cycles. Data gathered included demographics, tumor grade, stage, and response (partial response [PR], stable disease [SD], and progressive disease [PD]) on the basis of RECIST 1.1 criteria and 68Ga-dotatate positron emission tomography-computerized tomography pretreatment, after second and fourth treatment cycle, 6 months after fourth cycle, and at last follow-up. RESULTS: Fifty-one patients (51.6% women; age at diagnosis 66.0 ± 1.65 years), with pancreatic NET (PNET; n = 24), small intestine NET (n = 13), or other NET (n = 14), received PRRT, resulting in PR (n = 21), SD (n = 23), and PD (n = 3). Of the patients reaching PR after PRRT, most reached PR after two treatments (70.4%), with only 11.8% PR occurring between subsequent cycles (P =.001). Furthermore, patients with PR at mid-treatment had higher PR rates after PRRT completion than those with SD (P =.007). Patients harboring PNET who achieved PR had a more pronounced reduction of tumor burden in additional cycles than patients who did not (25.6% v 1.5%; P =.03, respectively). On the multivariable model, adjusted for grade and primary site, PR at mid-treatment evaluation was associated with a 20.9 adjusted odds ratio for additional PR at PRRT completion (P =.002). CONCLUSION: Mid-PRRT assessment predicts subsequent PRRT response in patients with WD-NET, especially those with PNET, informing personalized management and consideration of reduced bone marrow radiation exposure in high-risk patients. Limited response in 2 cycles of PRRT for NEN correlated with limited response in additional 2 cycles. [ABSTRACT FROM AUTHOR]

Multiple endocrine neoplasia 4 (MEN4) is a rare multiglandular endocrine neoplasia syndrome clinically hallmarked by primary hyperparathyroidism (PHPT), pituitary adenoma (PitAd), and neuroendocrine tumors (NET), clinically overlapping MEN1. The underlying mutated gene - CDKN1B, encodes for the cell-cycle regulator p27. Possible genotype-phenotype correlations in MEN4 have not been thoroughly assessed. Prompted by the findings in three Israeli MEN4 kindreds, we performed a literature review on published and unpublished data from previously reported MEN4/CDKN1B cases. Univariate analysis analyzed time-dependent risks for developing PHPT, PitAd, or NET by variant type and position along the gene. Overall, 74 MEN4 cases were analyzed. PHPT risk was 53.4% by age 60 years (mean age at diagnosis age 50.6 ± 13.9 years), risk for PitAd was 23.2% and risk for NET was 16.2% (34.4 ± 21.4 and 52.9 ± 13.9 years, respectively). The frameshift variant p.Q107fs was the most common variant identified (4/41 (9.7%) kindreds). Patients with indels had higher risk for PHPT vs point mutations (log-rank, P = 0.029). Variants in codons 94-96 were associated with higher risk for PHPT (P < 0.001) and PitAd (P = 0.031). To conclude, MEN4 is clinically distinct from MEN1, with lower risk and older age for PHPT diagnosis. We report recurrent CDKN1B frameshift variants and possible genotype-phenotype correlations.