Pheochromocytoma medical therapy
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ahmad Al Maradni, M.D. [2]
Overview
Treatment with alpha blockers (example: phenoxybenzamine) followed by beta blockers (example: atenolol) is required before surgery. Adjunctive chemotherapy and radiation are used in metastatic disease.
Medical Therapy
Any surgical option requires prior treatment with both the non-selective alpha adrenoceptor blocker (phenoxybenzamine) to counteract hypertension and the beta-1 adrenoceptor antagonist atenolol to reduce cardiac output. Given before surgery, these can also block the effect of a sudden release of adrenaline during tumour resection, which would otherwise endanger the anaesthetised patient.
TREATMENT — Once a pheochromocytoma is diagnosed, the patient should undergo surgery after appropriate medical preparation. Preoperative resolution of symptoms and normalization of blood pressure are predictors of an uncomplicated outcome [63].
Medical preparation for surgery — No universally accepted method of preparation for surgery in children with pheochromocytomas has been established. In our practice we generally use alpha-adrenergic blockade with phenoxybenzamine(Dibenzyline) unless contraindicated because of cardiopulmonary concerns. The starting dose of phenoxybenzamine in children is 0.25 to 1.0 mg/kg per day or 10 mg once daily; the dose is increased every few days until the patient's symptoms and blood pressure are controlled [10]. Due to increases in the cost of phenoxybenzamine, some clinicians may choose to a selective alpha-1 antagonist (eg, doxazosin, terazosin, prazosin).
On the second or third day of alpha-adrenergic blockade, patients are encouraged to start a diet high in sodium content because of the catecholamine-induced volume contraction and the orthostasis associated with alpha-adrenergic blockade. This causes intravascular volume expansion, which may be contraindicated in patients with heart failure or renal insufficiency.
After adequate alpha-adrenergic blockade has been achieved, beta-adrenergic blockade is initiated, which typically occurs two to three days preoperatively. The beta-adrenergic blocker should never be started first, because blockade of vasodilatory peripheral beta-adrenergic receptors with unopposed alpha-adrenergic receptor stimulation can lead to a further elevation in blood pressure. The clinician should exercise caution if the patient is asthmatic or has heart failure. Chronic catecholamine excess can produce a cardiomyopathy that may become evident with the initiation of beta-adrenergic blockade, resulting in acute pulmonary edema. Therefore, when the beta-adrenergic blocker is administered, it should be used cautiously and at a low dose. The dose is then increased as necessary to control the tachycardia. In most cases, the patient is ready for surgery in 10 to 14 days after starting the alpha-adrenergic blockade.
Although perioperative alpha blockade is widely recommended, a second regimen that has been utilized in adults at the Cleveland Clinic and France involves the administration of a calcium channel blocker for blood pressure control [64,65]. In a review of 113 adult patients who underwent removal of pheochromocytomas, fewer perioperative complications were observed in those not given alpha-adrenergic antagonists [64]. (See "Treatment of pheochromocytoma in adults", section on 'Calcium channel blockers'.)
A third approach is to administer metyrosine (alpha-methyl-para-tyrosine), which inhibits catecholamine synthesis by blocking the enzyme tyrosine hydroxylase. Metyrosine should be used with caution and only when other agents have been ineffective or if significant tumor manipulation is anticipated. Although some centers have used this agent routinely, most clinicians reserve metyrosine primarily for patients who cannot be treated with the combined alpha and beta-adrenergic blockade protocol because of intolerance or cardiopulmonary concerns. The starting dose of metyrosine in children is 125 mg (250 capsules can be reduced to 125 mg capsules by a pharmacist) once or twice daily, with an increase in dose as required or based on a target decline in fractionated metanephrines and catecholamines (unpublished personal experience). The use of metyrosine has also become more problematic because of increases in cost. (See "Treatment of pheochromocytoma in adults", section on 'Metyrosine'.)
Chemotherapy
Metastatic pheochromocytoma is treated with Averbuc protocol which is a combination of cyclophosphamide, vincristine, and dacarbazine.[1]
Radiation
131I-MIBG radiation therapy has been used for the treatment of MIBG-avid metastases.[1]
Contraindicated medications
Pheochromocytoma is considered an absolute contraindication to the use of the following medications:
References
- ↑ 1.0 1.1 National Cancer Institute. Physician Data Query Database 2015. http://www.cancer.gov/types/pheochromocytoma/hp/pheochromocytoma-treatment-pdq#link/_179_toc