#1703922 Laterality and Outcome in Pheochromocytoma: A Population-based Analysis

Pheochromocytomas are rare neuroendocrine tumors with an incidence ranging from 2-8 in a million and a prevalence of 1:2500 (1) Unilateral presentation is predominant, approximately 94.4% compared to bilateral tumor in 5-6% of patients (2). The concept of laterality of tumors in paired organs such as the breast and kidneys and its association with patients' outcomes have been reported in the literature (3,4) It remains unknown if this exists in pheochromocytoma (PCC). We aimed to examine this phenomenon in PCC using nationally representative data. Cases of PCC were obtained from the Surveillance, Epidemiology, and End Results Program (SEER) Research Plus 17 database (2000-2020) using the International Classification of Diseases (ICD-0-3) code 8700. Cases with bilateral PCC and without pathologic diagnosis were excluded. Data obtained included age, race/ethnicity, laterality, tumor stage, metastatic site (liver, brain, or bone) treatment type, and survival in months. Patients' characteristics were compared between right and left PCC using descriptive statistics. Multivariable regression analyses were done to determine independent predictors of mortality in PCC tumors. 329 cases of PCC were obtained from the SEER database, with a right and left distribution of 48.3% vs 51.7%, respectively. There was no significant difference in age, sex, race, tumor size, stage, metastatic sites to the brain, lung, and liver, and treatment characteristics between right and left PCC tumors. Median survival was similar (59 months [IQR: 19-126] vs 57 months [13-122]). Predictors of mortality were older age (50 years; right: aOR =1.80 (1.01-3.21, p= 0.045) and left: aOR=2.27 (1.31-3.93, p=0.003) and advanced stage of the tumor (distant; right: aOR = 5.09 (2.00-12.95, p=0.001) and left: aOR= 6.48 (2.59-16.23, p< 0.001). Left PCC tumors diagnosed between 2011 and 2020 were independently associated with increased odds of mortality [aOR 2.01 (1.19-3.40, p=0.009)] unlike right PCC tumors, where there was no association with year of diagnosis. There was no association between sex, race, tumor size, and stage, metastatic site or treatment characteristics, and mortality on both sides of PCC tumors. While laterality has been reported and established in some paired organs, such a concept appears less significant in PCC tumors. However, the prognosis in left PCC tumors seems to have worsened in the last decade compared to the previous. Further studies are needed to explore the reasons for this observation.