PET scan assessment of chemotherapy response in metastatic paraganglioma

Paragangliomas are indolent tumors that arise from the chief cells of the paraganglia in the head and neck, mediastinum, and retroperitoneal regions. Less than 10% of paragangliomas metastasize. Paragangliomas are known to regress slowly and usually partially after radiation therapy, which has been attributed to the development of fibrosis within the abundant vascular elements of the tumor. Positron emission tomography (PET) scanning was used to monitor a 33-year-old woman with recurrent paraganglioma of the carotid body with lung and bone metastases before and after chemotherapy with cyclophosphamide, doxorubicin (Adriamycin), and dacarbazine. The patient derived clinical benefit from chemotherapy, with marked improvement of her systemic and respiratory symptoms, improvement of cancer-related anemia, and normalization of chromogranin A levels. A response was demonstrated on PET scan with decreased [18F] fluoro-2-deoxy-d-glucose uptake after chemotherapy, but no significant changes were detected on serial computed tomography (CT) scans. The patient has remained free of disease progression 24 months after chemotherapy completion. It is suggested that metabolic imaging with PET scans is superior to anatomical imaging with CT scans for the monitoring of patients with paragangliomas.