The who, when, and why of primary adrenal malignancies: Insights into the epidemiology of a rare clinical entity

Background: Primary malignancies of the adrenal glands are rare. Epidemiologic assessment of primary adrenal malignancies is lacking and has been limited to case reports and series. Population-level data can provide a better understanding of the incidence, distribution, and prognostic factors associated with these rare malignancies. Methods: The Surveillance, Epidemiology, and End Results database (1973-2013) was queried for all patients who were diagnosed with primary adrenal malignancies, categorized in 5 histologic groups: adrenocortical carcinoma (ACC), pheochromocytoma and paraganglioma (PH), neuroblastoma (NE), non-Hodgkin lymphoma (NHL), and sarcoma (SA). Age-adjusted incidence, distribution trends, and cancer-specific survival (CSS) for each group were analyzed. Results: In total, 4695 patients with primary adrenal malignancies were identified, including 2057 with ACC, 512 with PH, 1863 with NE, 202 with NHL, and 61 with SA. The age-adjusted incidence of all 5 histologic subtypes was rising. Age at presentation differed substantially by histologic group: NE was the most prevalent during the first decade of life, whereas ACC predominated after age 30 years, and NHL outnumbered PH after age 70 years. Patient-specific factors were not associated with advanced disease at the time of presentation. The 5-year CSS rate for each histologic subtype was 38% for ACC, 69% for PH, 64% for NE, 38% for NHL, and 42% for SA. Survival outcomes for patients with ACC, NHL, PH and SA remained unchanged over the 40-year study period. Multimodal therapy was associated with higher CSS in patients with NE. Conclusions: This first population-level analysis of all primary adrenal malignancies provides important initial data regarding presentation and clinical outcomes. Notably, except for patients with NE, the survival of patients with these rare cancers has not improved over the past 40 years.