Clinical features and outcomes of metastatic pheochromocytoma treated by cytotoxic chemotherapy

Cytotoxic chemotherapy, including cyclophosphamide, vincristine, and dacarbazine (CVD) therapy, is widely used to treat metastatic pheochromocytoma and paraganglioma. Because these diseases are rare, studies are needed to establish treatment strategies. This was a single-center and retrospective study to analyze the efficacy of chemotherapy for patients with metastatic pheochromocytoma and paraganglioma diagnosed in 1983-2020. Clinical characteristics, tumor volume response, biochemical response based on catecholamine level, overall survival, and progression-free survival were evaluated. Patients with a complete response or partial response in tumor volume or catecholamine level were classified as responders. Sixteen patients were administered chemotherapy for a median of 16.5 cycles (interquartile range, 10-42). The tumor volume response was classified as follows: partial response (N = 4), stable disease (N = 9), and progressive disease (N = 3) (disease control rate = 81%). The biochemical responses were as follows: complete response (N = 2), partial response (N = 5), no change (N = 3), and progressive disease (N = 1) (disease control rate = 91%). The 5-year survival rate was 50% (95% confidence interval [CI], 21-74%) and median overall survival was 4.4 years (95% CI, 2.4 years not reached). Overall survival and progression-free survival between responders and nonresponders were not statistically different. One patient developed myelodysplastic syndrome during CVD therapy. In conclusion, chemotherapy achieved disease control among more than half of patients, although survival did not differ between responders and nonresponders. Further fundamental research and prospective trials arc needed to analyze the efficacy of CVD therapy.