By David Douglas

NEW YORK NOV 06, 2007 (Reuters Health) - The calcimimetic, cinacalcet HCl, reduces the serum calcium concentration in inoperable parathyroid carcinoma, a condition characterized by severe hypercalcemia.

“Cinacalcet is an exciting addition to the treatment options for patients with inoperable parathyroid cancer,” lead investigator Dr. Sonni J. Silverberg told Reuters Health. “Although the drug does not treat the underlying disease, it does effectively reduce the serum calcium level in most patients with this difficult to treat disease.”

In the October issue of The Journal of Clinical Endocrinology and Metabolism, Dr. Silverberg of Columbia University College of Physicians & Surgeons, New York and colleagues note that morbidity and mortality associated with parathyroid carcinoma result primarily from parathyroid hormone (PTH)-driven severe hypercalcemia, and control of hypercalcemia becomes a priority once surgical options are exhausted.

Cinacalcet has shown promise in this regard and the researchers evaluated the agent in an open-label study of 29 patients. At baseline, the mean serum calcium level was 14.1 mg/dL and PTH was also markedly elevated.

Cinacalcet was started at 30 mg twice daily and doses were increased depending on patient tolerance and the serum calcium level. Over the course of 16 weeks, titration continued until the dose reached 90 mg four times a day or serum calcium fell to 10.0 mg/dL or less.

At the end of the titration period, 62% of patients showed a reduction of 1 mg/dL or more in serum calcium level, and the mean level decline to 12.4 mg/dL.

The greatest drop was seen in patients with the greatest baseline levels. “Dramatic reductions,” say the investigators, “were observed in the most severely hypercalcemic patients, supporting the ability of cinacalcet to control hypercalcemia in those with greatest need.”

PTH levels decreased by 4.6%, but this reduction was not significant.

Overall, the researchers conclude that the agent “effectively reduces hypercalcemia in approximately two thirds of patients … and may represent an important new treatment option.”

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