12576 Two Cases Of Radionuclide Treatment Of Inoperable Benign Pheochromocytomas Due To Cardiopathies: Clinical Improvement Is Possible

Abstract Disclosure: S.Y. Abe: None. C. Vieira de Souza: None. J.J. Cerci: None. A.M. Rodrigues: None. Background: Pheochromocytomas are more prevalent in cyanotic cardiopathies, and cardiovascular problems can be a consequence of excess catecholamines. Diagnosis could be delayed because symptoms overlap, and treatment could be a challenge because of increased surgical risk. Other therapeutic options are necessary.Clinical Case 1: A 28-year woman with congenital cyanotic heart disease (transposition of the great vessels) submitted to surgery in the first year of life and in the age of 10, presenting with arrhythmia (CDI for 8 years), pulmonary hypertension and heart failure, in use of many medications including betablockers and on oxygen therapy at night, was diagnosed with pheochromocytoma in an abdominal CT scan for investigation of intestinal sub occlusion. There was a hyper vascular mass of 37 x 65 x 54 mm in the right adrenal gland and a left paravertebral nodule of 1,4 x 1,2 cm, and metanephrine levels were extremely high: 4260 mcg/24h (280), normetanephrines 1993 mcg/24h (732). She had had symptoms of hypertension crisis, perspiration, palpitations, nausea, vomiting and constipation previously but pheochromocytoma was not suspected. Surgical treatment was contraindicated. Alpha-blockade was added. 200 mCi (7.4 GBq) MIBG -I 131 was administered in January 2023. In the follow-up she gained 10 kg (22 pounds), blood pressure and heart rate were controlled, and she improved functionally. Metanephrine levels decreased and normalized while normetanephrine levels increased (177,3 mcg/24h and 3726,7 mcg/24h, respectively, in March 2024). The right mass reduced to 32x60x56mm and the left mass to 1,2 x 0,9 cm.Clinical Case 2: A 87-year man with hypertension, left ischemic stroke in 2017 and right ischemic stroke in 2021, patent foramen ovale closure in 2021,and hypertension crisis/palpitations during defecation, was diagnosed with pheochromocytoma in a CT scan, confirmed by MRI (hyper vascular left adrenal mass, hyperintense in T2, 61x60x50mm) and urinary metanephrines: metanephrines 1837 mcg/24hours ( 230) and normetanephrines 542 mcg/24h (490). Surgical treatment was contraindicated. Alpha-blockade was added. It was administered 200 mCi (7.4 GBq) MIBG -I 131 in June 2022, since uptake was good, but the response was not, and metanephrine levels increased: plasmatic metanephrines 8,6 to 11,6 nmol/l (0,5) and normetanephrines 1,6 to 3,1 nmol/l (0,9). He also had an intense uptake of DOTA-TATE- Ga 68, so he received 6 applications of DOTA-TATE - Lu 177 (7.4 GBq) in 2023, which resulted in a decrease in metanephrine levels (to 6 nmol/l) and increase in normetanephrines (to 2,4 nmol/l). Blood pressure and heart rate were controlled. Conclusion: These two cases demonstrate effectively radionuclide treatment with clinical improvement associated with biochemical shift from metanephrine to normetanephrine excess. Presentation: 6/1/2024