Pheochromocytomas are uncommon tumors that arise from cells of the sympathetic nervous system and may secrete catecholamines (adrenalin). Such tumors are usually found within one or both adrenal glands (90%), but may arise in other areas of sympathetic nerve cells, and are then called paragangliomas. About 10% are found to be malignant at the time or immediately after the primary tumor is discovered. Another 5% of individuals with pheochromocytomas are later found to have malignant or recurrent disease. Interestingly, about 10% of such patients do not have hypertension at all or may have hypertension only during surgical procedures or very intermittently at which time a hypertensive crisis can occur.
Pheochromocytomas are a rare cause of hypertension, being the underlying cause of only about .01% of cases of high blood pressure. The manifestations of pheochromocytoma are varied and often not particularly specific and it is easy to understand why such a rare tumor may not be diagnosed immediately by even the most astute physician. Headache, perspiration or palpitation are symptoms found in 90% of such patients. Anxiety, tremor, high blood sugar, nausea, thoracic or abdominal pains, weakness, weight loss, shortness of breath, visual disturbances and heat intolerance are other occasional symptoms. Patients can also sometimes present with confusion or psychosis, constipation, tingling sensations, seizures, or high blood counts as well as Raynaud’s phenomenon. Ironically, patients can also have a slow heart beat (bradycardia) or hypotension, particularly when standing up suddenly.
Treatment of pheochromocytomas involves blocking the effect of catecholamines with an alpha adrenergic blocker such as phenoxybenzamine. After adequate block, it then becomes safe to surgically remove the pheochromocytoma or paraganglioma. Even relatively large pheochromocytomas have been successfully removed at UCSF Medical Center via laparoscopy. Patients with metastatic or recurrent pheochromocytoma or paraganglioma present a difficult problem. Chemotherapy has not been particularly successful. Radiation therapy can be given to bone metastasis. Dr. Fitzgerald is the principal investigator in a clinical research protocol at UCSF Medical Center which is approved by the Committee on Human Research. This protocol involves treating patients with metastatic or recurrent pheochromocytoma (and similar tumors) which take up MIBG (metaiodobenzylguanadine). I-131 MIBG can be given to such patients in very high doses. The tumor takes up the isotope and delivers a dose of radiation to itself.
Our UCSF I-131 MIBG protocol for malignant pheochromocytomas and paragangliomas involves extensive pre and post-treatment evaluations. Peripheral stem cell harvests are required since bone marrow damage from the radiation may be otherwise present and the harvesting of autologous stem cells from the patients then allows reinfusion and regrowth of bone marrow damaged by the radioisotope therapy. Patients need to be in relatively good physical condition to withstand this treatment. They require confinement in a lead-shielded room. The radiation therapy and adjuvant medication does cause nausea. The entire treatment course takes about 7 days.
I-131 MIBG treatment is currently considered helpful but is unlikely to be curative, although several cases of apparent cures have been reported. Symptomatic or objective responses to treatment occur in over 70% of patients. Treatment responses have been best with soft tissue metastases. Bone metastases have responded less favorably.
A major consideration with this form of therapy for malignant pheochromocytomas involves logistics and cost. It takes about two to three months to set up such a treatment and only two such treatments can be performed monthly at UCSF due to nuclear safety precaution requirements. The high expense of this procedure is also an impediment to treatment since the entire cost for the nuclear isotope preparation, hospitalization, pre-treatment stem cell harvest, and other fees run up to $50,000 for a single treatment.
Physicians who have patients who may be candidates for this treatment protocol are asked to contact Dr. Paul Fitzgerald directly.