Background: Catecholamine and metanephrine levels usually normalize after complete surgical removal of pheochromocytomas (PCC) and paragangliomas (PGL). Little known about the relationship between decline in catecholamine and metanephrine levels and changes in systolic blood pressure (SBP) and SBP variability following tumor resection.
Methods: A prospective observational study of patients evaluated at the Penn Neuroendocrine Tumor Program for suspected PCC/PGL between January 2014 and December 2016. Plasma and urine catecholamine and metanephrine levels were obtained and patients underwent 24-hour ambulatory blood pressure monitoring 1-3 weeks prior to tumor resection. In patients with histologically-confirmed secretory PCC/PGL, testing was repeated 6-8 weeks post-operatively.
Results: 32 patients met inclusion criteria. Median age was 56 years, with 44% males (n=14), 78% Caucasians (n=25), and median body mass index 25.5 kg/m2. 56% of patients (n=18) were on alpha-blockade at baseline. Compared to pre-operative values, there was a significant decline in post-operative 24-hour mean SBP (133.1 vs. 127.4 mmHg, p=0.036), 24-hour SBP average real variability ([ARV] 10.0 vs. 9.0, p=0.031), 24-hour mean pulse pressure (54.5 vs. 51.6 mmHg, p=0.012), and 24-hour mean heart rate (78.5 vs. 74.0 bpm, p=0.023). Greater decline in 24-hour SBP was associated with a greater decline in plasma normetanephrine (Spearman’s rho [r]=-0.43, p=0.017), plasma norepinephrine (r=-0.59, p=0.002), and urine normetanephrine (r=-0.66, p=0.001). Greater decline in 24-hour SBP ARV was associated with a greater decline in plasma norepinephrine (r=-0.46, p=0.024). These associations were stronger among patients who were not on alpha-blockade at baseline (SBP and plasma normetanephrine r=-0.73, p=0.005; SBP and plasma norepinephrine r=-0.71, p=0.015; SBP and urine normetanephrine r=-0.76, p=0.006; ARV and plasma norepinephrine r=-0.71, p=0.047).
Conclusion: Decline in 24-hour SBP and SBP variability was directly associated with degree of improvement in catecholamine and metanephrine levels after PCC/PGL resection, and more evident when alpha-blockade was absent during baseline testing.