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Pheochromocytoma Size Correlates Directly With Catecholamine Secretion Levels
*Lee M Stratton, *Brian Ruhle, *Kelvin Memeh, *Edwin Kaplan, Peter Angelos, *Xavier M Keutgen
The University of Chicago, Chicago, IL

OBJECTIVE(S): Elevated plasma or urinary metanephrine and catecholamine levels at least 3 fold upper limit of normal (ULN) are considered diagnostic for pheochromocytomas. We sought to determine whether pheochromocytoma size correlates with biochemical activity as this could influence clinicians’ decision making for timing of surgical intervention and preoperative alpha blockade.
METHODS: A review of 56 consecutive patients from 2013-2020 undergoing adrenalectomy for pheochromocytoma was performed. Collected data included maximal lesion diameter based on preoperative CT or MRI, available plasma and urine metanephrine and/or catecholamine levels, demographic variables and presence of typical paroxysmal symptoms. Analysis was performed using Stata software and a curve of best fit was made using a logarithmic transformation model of the tumor size.
RESULTS: Fifty-five patients were included in the analysis of which 38 were females and 17 males. Average patient age was 56 ± 15. Due to variability in referral practices, 27 patients had documented 24-hour urine metanephrine, 22 had 24-hour urine catecholamine, and 48 had fractionated plasma metanephrine levels available for review. For comparison between these groups, values were converted to fold change compared to the upper limit of normal and the highest value was chosen for analysis (mean 14.8 ± 24.8; median 8.3). Mean tumor size was 3.8 ± 2.1 cm in greatest dimension. A logarithmic transformation model showed a direct correlation between tumor size and biochemical activity (R2 0.54, √MSE 0.77). Furthermore, biochemical activity increased by 49% per cm increase in tumor size (95% CI 34.8-65.3, p = <0.001). Tumor size at which pheochromocytomas produced catecholamines and/or metanephrine levels > 3 fold ULN was determined to be 1.45cm or greater. A total of 33 patients (61%) had documented paroxysmal symptoms, but there was no significant correlation between tumor size or biochemical activity and symptoms. There was also no significant correlation between tumor laterality, patient age or sex and tumor size or biochemical activity.
CONCLUSIONS: Pheochromocytoma size directly correlates with the degree of biochemical activity and tumors ≥1.45cm produce catecholamine levels 3 times ULN. These findings may allow clinicians to adjust timing of operative intervention and preoperative blockade.


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