Inherited mutations in pheochromocytoma and paraganglioma: why all patients should be offered genetic testing

Abstract

Background: Pheochromocytomas (PCC) and paragangliomas (PGL) are neuroendocrine tumors that, although rare, are an important cause of secondary hypertension because of the high morbidity and mortality. PCC/PGL are still thought of as the "tumor of tens," with 10 % being hereditary; however, recent population based studies suggest that up to 32 % of patients have a germline mutation in one of the known common susceptibility genes (including NF1, VHL, RET, SDHB, SDHD, and SDHC). Despite this, most patients in the United States are not referred for clinical genetic testing by their physicians. We aimed to examine the mutation prevalence in a clinic-based population in the United States.

Methods: We performed a retrospective chart review of 139 consecutive patients with PCC/PGL from the medical genetics clinic at the hospital of the University of Pennsylvania from January 2004 through February 2012.

Results: We found a 41 % overall mutation detection rate. Twenty-six percent of the cohort had a mutation in the SDHB or SDHD genes. Of patients with at least one PGL tumor outside the adrenal gland, 53 % had an identified mutation.

Conclusions: Forty-one percent of the cohort had a heritable mutation. The most commonly mutated gene was SDHB, which carries the highest risk of malignancy. These data, together with American Society of Clinical Oncology guidelines suggesting that genetic testing be performed if the risk of a hereditable mutation is at least 10 % or if it will affect medical management, strongly suggest that all patients with PCC/PGL should undergo clinical genetic testing.

Figure 1

Clinical Genetic Testing Algorithm. Clinical genetic testing was performed in a step wise manner based on clinical assessment by a medical geneticist. Deviations from this general algorithm could occur based on individualized patient care. During the majority of the study period, a PCC/PGL panel of gene testing and individual testing for SDHAF2, TMEM127 and MAX was not readily available. Immunohistochemistry for SDHB also was not widely available during most of the study period and did not play a role in the testing algorithm. DA/MT – dopamine/methoxytyramine; MN – metanephrine