Hereditary pheochromocytoma (PCC) is often caused by germline mutations in one of nine susceptibility genes described to date, but there are familial cases without mutations in these known genes. We sequenced the exomes of three unrelated individuals with hereditary PCC (cases) and identified mutations in MAX, the MYC associated factor X gene. Absence of MAX protein in the tumors and loss of heterozygosity caused by uniparental disomy supported the involvement of MAX alterations in the disease. A follow-up study of a selected series of 59 cases with PCC identified five additional MAX mutations and suggested an association with malignant outcome and preferential paternal transmission of MAX mutations. The involvement of the MYC-MAX-MXD1 network in the development and progression of neural crest cell tumors is further supported by the lack of functional MAX in rat PCC (PC12) cells and by the amplification of MYCN in neuroblastoma and suggests that loss of MAX function is correlated with metastatic potential.

Germline mutations are rare in apparently sporadic probands diagnosed after age 40 yr (3.9% in our series) and mainly involve SDHB. Therefore, we recommend prioritizing SDHB genetic testing in patients developing isolated tumors at any age, especially those with extraadrenal location or malignant behavior.

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Pheochromocytoma and paraganglioma are rare neuroendocrine tumors that arise in the adrenal medulla and the extra-adrenal paraganglia, respectively. Inheritance of these tumors is mainly a result of mutations affecting the VHL, RET, NF1, and SDH genes. Germ-line mutations of the SDH genes have been found to account for nearly 10% of apparently sporadic cases. Nevertheless, alterations other than point mutations have not yet been well characterized. In this study, we investigated the frequency of gross SDH deletions in 24 patients who tested negative for point mutations and had at least one of the recommended features for genetic testing. For this purpose, we used a technique that is easy to implement in the lab to specifically detect gross deletions affecting SDHB, SDHC, and SDHD. We identified 3 heterozygous SDHB deletions (3/24) in 3 independent cases with paraganglioma: 1 whole SDHB deletion and 2 deletions exclusively affecting exon 1. These latter mutations match the unique gross deletion previously reported, indicating this region could be a hot spot for gross SDHB deletions. It seems likely that these alterations can account for a considerable number of both familial and apparently sporadic paraganglioma cases. Although this is the first report describing the presence of gross deletions in patients with apparently sporadic paragangliomas, the extra-adrenal location of the tumor seems to constitute a determining factor for whether to include these patients in genetic testing for gross deletions in the SDHB gene.

PURPOSESomatostatin analogs (SSAs) are recommended for the first-line treatment of most patients with well-differentiated, gastroenteropancreatic (GEP) neuroendocrine tumors; however, benefit from treatment is heterogeneous. The aim of the current study was to develop and validate a progression-free survival (PFS) prediction model in SSA-treated patients.PATIENTS AND METHODSWe extracted data from the Spanish Group of Neuroendocrine and Endocrine Tumors Registry (R-GETNE). Patient eligibility criteria included GEP primary, Ki-67 of 20% or less, and first-line SSA monotherapy for advanced disease. An accelerated failure time model was developed to predict PFS, which was represented as a nomogram and an online calculator. The nomogram was externally validated in an independent series of consecutive eligible patients (The Christie NHS Foundation Trust, Manchester, United Kingdom).RESULTSWe recruited 535 patients (R-GETNE, n = 438; Manchester, n = 97). Median PFS and overall survival in the derivation cohort were 28.7 (95% CI, 23.8 to 31.1) and 85.9 months (95% CI, 71.5 to 96.7 months), respectively. Nine covariates significantly associated with PFS were primary tumor location, Ki-67 percentage, neutrophil-to-lymphocyte ratio, alkaline phosphatase, extent of liver involvement, presence of bone and peritoneal metastases, documented progression status, and the presence of symptoms when initiating SSA. The GETNE-TRASGU (Treated With Analog of Somatostatin in Gastroenteropancreatic and Unknown Primary NETs) model demonstrated suitable calibration, as well as fair discrimination ability with a C-index value of 0.714 (95% CI, 0.680 to 0.747) and 0.732 (95% CI, 0.658 to 0.806) in the derivation and validation series, respectively.CONCLUSIONThe GETNE-TRASGU evidence-based prognostic tool stratifies patients with GEP neuroendocrine tumors receiving SSA treatment according to their estimated PFS. This nomogram may be useful when stratifying patients with neuroendocrine tumors in future trials. Furthermore, it could be a valuable tool for making treatment decisions in daily clinical practice.