Development of a formula to predict parathyroid carcinoma in patients with primary hyperparathyroidism.

BACKGROUND: Cure of parathyroid carcinoma (PC) requires initial en bloc resection, including resection of all tumor-bearing tissue, with hemithyroidectomy and dissection of the central lymph node compartment. Unfortunately, no reliable preoperative criteria have yet been assessed to indicate a high likelihood of PC. Thus, the aim of the present study was to develop a formula to indicate preoperatively the presence of PC.

METHODS: A prospective database of 1,363 patients with primary hyperparathyroidism (pHPT) was screened for patients with PC. Age, gender, surgical procedures, laboratory data, and follow-up results were evaluated and compared to a group of patients with benign pHPT. Based on preoperative serum calcium (Ca) and parathyroid hormone (PTH) levels, as well as patients' age at the time of diagnosis, a formula was developed by a multivariate logistic model that estimates the individual risk for PC.

RESULTS: Between 1987 and 2008, 19 patients with PC were identified. Ca (3.8 ± 0.3 vs 2.9 ± 0.3 mmo/l; p = 0.0002) and PTH levels (1,250 ± 769 vs 194 ± 204 pg/ml; p = 0.0030) were significantly higher in patients with PC than in those with benign pHPT. Patients with PC were also significantly younger than patients with benign pHPT (48.9 ± 12.1 vs 59.1 ± 13.8 years; p < 0.05). With a ≥5 % probability that a given patient suffered from PC, the sensitivity and specificity to identify the disease were 100 and 30 %, respectively, with the new Ca, PTH, and age based logarithmic formula.

CONCLUSIONS: The new logarithmic formula can be used to calculate the individual risk for PC. If the calculated individual risk exceeds 5 %, en bloc resection seems to be justified to provide long-term cure in case of PC.