Prognostic factors and staging systems in parathyroid cancer: a multicenter cohort study

Parathyroid carcinoma (PC) is an uncommon disease that generally is detected postoperatively and traditionally is associated with a poor prognosis. Our purpose was to evaluate treatment outcomes, prognostic factors, and usefulness of some proposed staging systems for this disease.

A multicenter review of patients with surgically resected PC was performed, led by the Spanish Association of Surgery. All surgical units affiliated with its endocrine surgery section were invited to answer a questionnaire that collected several hospital-related, clinical, biochemical, operative, pathologic, and follow-up data. Their relationships with prognosis were assessed by both univariate and multivariate analysis, as well as the effectiveness of three staging systems for parathyroid carcinoma.

Of the 6,863 patients undergoing parathyroidectomy, 62 (0.9%) had PC. Of them, 12 (19.3%) died, in 5 cases (8%) because of disease, and 14 (22.6%) suffered recurrence, after a median follow-up of 55 months. The most predictive independent variables on tumor recurrence were intraoperative tumor rupture (hazard ratio [HR] 6.22; 95% confidence interval [CI] 1.19-32.36; P = .030); the presence of mitotic figures within tumor parenchyma cells (HR 4.76; 95% CI 1.24-18.21; P = .022); and allocation in class III according to Schulte differentiated staging classification (HR 5.23; 95% CI 1.41-19.31; P = .013). As to disease-specific survival, poor outcomes were associated with intraoperative tumor rupture (HR 58.71; 95% CI 2.39-1,439.96; P = .013) and distant recurrence (HR 38.74; 95% CI 3.44-435.62; P = .003).

In addition to factors associated with tumor histopathology and stage, prognosis of PC is greatly influenced by surgeon's performance, which emphasizes the importance of preoperative diagnosis.