Phaeochromocytomas (PCC) and paragangliomas (PGL) are rare tumours derived from the sympathetic or parasympathetic paraganglia. They characteristically secrete catecholamines (noradrenaline/adrenaline/dopamine), which are metabolised to the metanephrines (normetadrenaline/metadrenaline/3-MT respectively). These tumour markers can be detected in acidified 24-h urine collections as first-line investigative tests. Plasma 3-MT has been characterised as a biomarker of metastatic PGL/PCC. In the present study, we aim to characterise the diagnostic utility of urine 3-MT.
Objectives: To evaluate the diagnostic utility of urine 3-methoxytyramine (3-MT) in the diagnosis of metastatic PCC and PGL disease.
Design and setting: A retrospective study using 44 patients with no known PCC or PGL disease (34 being screened for hypertension, ten with previous disease which was completely resected) compared to 21 patients with known PCC or PGL disease (nine head and neck, nine abdominal including PCC, three thoracic). Those patients with PCC/PGL were further classified into those with metastatic (7) and without metastatic disease (14). Acidified 24 h urine samples were assessed for 3-MT levels using an in-house HPLC method.
Results: ROC curve analysis of 3-MT excretion for the diagnosis of PCC/PGL showed that the area under curve (AUC) was 0.8226. Mean (±S.D.) levels of 3-MT in those with PCC/PGL was 3.83±7.08 μmol/24 h and in those without 0.82±0.31 μmol/24 h (P<0.0001, MannWhitney U test). Comparing those with metastatic disease to those without, the ROC-AUC was 0.8367. Mean (±S.D.) levels of 3-MT in metastatic disease was 8.99±10.96 μmol/24 h and without metastatic disease 1.25±0.52 μmol/24 h (P=0.0153, MannWhitney U test).
Conclusions: 3-MT is a good biomarker for the diagnosis of PCC or PGL disease, and particularly for distinguishing metastatic vs non-metastatic disease.