Telomerase activation and ATRX mutations are independent risk factors for metastatic pheochromocytoma and paraganglioma

Purpose: Pheochromocytomasand paragangliomas(PPGL) are rare neuroendocrine tumors. While most PPGL are benign, up to 20% may become metastatic with SDHB- and FH -mutated tumors showing the higher risk. We aimed at determining the contribution of immortalizationmechanisms to metastatic progression. Experimental design: Immortalizationmechanisms were investigated in 200 tumors. To identify telomerase(+) tumors we analyzed genomic alterations leading to transcriptional activation of TERT comprising promoter mutations, hypermethylation and gain copy number. To identify tumors that activated the alternative lengthening of telomere (ALT) mechanism, we combined analyses of telomere length by slot blot, telomere heterogeneity by telomere FISH, and ATRXmutations by next-generation sequencing. Univariate/multivariate and metastasis-free survival (MFS) and overall survival (OS) analyses were carried out for assessment of risk factors and clinical outcomes. Results: Only 37/200 (18.5%) tumors achieved immortalization. Telomeraseactivation occurred in 12 metastatic tumors, and was prevalent in SDHB-mutated paragangliomas( P = 2.42e-09). ALT features were present in 25 tumors, mostly pheochromocytomas, regardless of metastatic status or molecular group ( P = .169), yet ATRXmutations were found preferentially in SDHB/ FH -mutated metastatic ( P = .0014). Telomeraseactivation and ATRXmutations were independent factors of poor prognosis: MFS ( hazard ratio, 48.2 and 33.1; P = 6.50E-07 and 1.90E-07, respectively); OS ( hazard ratio, 97.4 and 44.1; P = 4.30E-03 and 2.00E-03, respectively) and were associated with worse MFS and OS (logrank tests P ATRXmutations could be used to identify metastatic PPGL, particularly in tumors at high-risk of progression.