Functional parathyroid carcinoma: Long-term treatment outcome and risk factor analysis.

Background: This study was conducted to evaluate the long-term outcome of surgical treatment in patients with functional parathyroid carcinoma and to clarify factors determining prognosis.
Methods: A retrospective review of 38 patients with parathyroid carcinoma was performed. The Ki-67 index was evaluated in 29 cases. Disease-free survival and cause-specific survival estimated using the Kaplan-Meier method were analyzed, and the median follow-up period was 119 months.
Results: Fifteen patients developed persistent or recurrent parathyroid carcinoma, and 9 patients died of the disease. Twenty-one of 41 reoperations normalized the serum calcium level for at least 6 months. Univariate and multivariate analyses showed that locoregional tumor extension at initial operation and Ki-67 index >or=5% were significant factors affecting cause-specific survival (P = .0008, P = .05) and disease-free survival (P = .0005, P = .005), respectively. Five of 6 patients whose tumor showed a Ki-67 index >or=10% developed recurrence within 3 years after initial operation, and 4 died of the disease.
Conclusions: Parathyroid carcinomas with locoregional extension at initial surgery have potential for recurrence. Our data suggest that aggressive surgical resection of recurrent parathyroid carcinoma is beneficial for palliation of hypercalcemia in selected patients. Ki-67 staining may be a valuable prognostic factor for patients with parathyroid carcinoma, especially as tumors with indices greater than 10% are more likely to recur in the early postoperative period.