Paraneoplastic secretion in parathyroid carcinoma: serum hCG as a tumor marker

Introduction
Parathyroid carcinoma (PCa) is a rare presentation of primary hyperparathyroidism (PHPT), accounting for less than 1 % of cases. Differentiating parathyroid cancer from adenoma is clinically challenging. Rubin et al (2008) et al. suggested that urinary hCG might be a marker of disease progression in PCa. In this study, we aimed to investigate whether the hCG+β kit from Roche Diagnostics could distinguish PCa patients from PHPT.

Material and methods
We studied a series of 8 patients suffering from advanced PCa, referred to the CHU de Liege. A control group of 20 PHPT patients was used as comparative. hCG+β kit on Cobas (Roche Diagnostics) uses 2 monoclonal antibodies that recognize holo-hCG, nicked hCG, β-core fragment and free β-subunit. Limits of hCG detection and quantification are <0.1 and <0.6 mUI/mL. In non pregnant and postmenopausal women and in men, hCG (p95) is <1 (5.3), <7 mUI/mL (8.3) and <2 (2.6) mUI/mL, respectively.

Results.
The 8 PCa patients (3 women) presented high serum hCG values at: 1.29, 3.46, 5.7, 24.2, 31.2, 34.1, 36.5 and 164 mUI/mL. Values of 1.29 and 3.46 were obtained in 2 postmenopausal women. The lowest value was presented by the only still alive patient. There was a significant correlation (r=0.786; ρ <0.05) between hCG and PTH and a borderline correlation (r=0.750; ρ =0.05) between hCG and calcium concentrations. All PHP patients presented undetectable hCG values.

Conclusions
These results suggest that serum hCG might have the potential to discriminate between parathyroid adenomas and carcinomas, with a sensibility of 75% (6/8) and a specificity of 100% (0/20). The only patient still alive presented the lowest hCG values. If hCG could be predictive of PCa survival needs to be studied in a larger series of patients.