Sep. 10, 2007 New research accepted for publication in the Journal of Clinical Endocrinology & Metabolism (JCEM) reveals that the drug cinacalcet HCl (cinacalcet) may effectively reduce the dangerous accumulation of calcium in the blood that typically accompanies parathyroid cancer.
This drug therapy could provide a new and effective medical treatment option for patients with inoperable parathyroid carcinoma (cancer).
“Patients with inoperable parathyroid cancer typically have to contend with extremely elevated levels of calcium in their blood, which can lead to mental confusion, dehydration, kidney damage and ultimately death,” said Dr. Shonni Silverberg of the College of Physicians and Surgeons at Columbia University in New York City and senior author of the study.
Management of inoperable parathyroid carcinoma has been a challenge due to the lack of effective medical therapy. In addition to treating the cancer, doctors also often need to treat hypercalcemia, or excess calcium in the blood, which can be more harmful than the parathyroid cancer itself.
“Until now, the therapeutic choices for patients with inoperable parathyroid cancer have been extremely limited,” said Silverberg. “Cinacalcet offers an important option for treating hypercalcemia in patients with metastatic disease after surgical options have been exhausted.”
Cinacalcet is a drug that mimics how calcium acts on organ tissues. It is used to treat hyperparathyroidism, or elevated parathyroid hormone levels, because it reduces parathyroid cell hormone secretion by binding to the calcium-sensing receptor on parathyroid cells.
The study was conducted at 15 centers in the United States and Europe. Twenty-nine patients with parathyroid cancer were enrolled. The study design included a variable-length titration (treatment with varying doses) phase and a maintenance phase. During the titration phase, cinacalcet was administered to patients until their serum calcium concentration were within normal levels (<10 mg/dL), the dose reached 90 mg, or the patient experienced adverse effects.
During the maintenance phase, dose increases were administered if needed, and doctors were permitted to prescribe treatments deemed necessary to provide adequate supportive care.
Serum calcium was reduced by >1 mg/dL in 62 percent of patients. The greatest reductions in serum calcium were observed in patients with highest baseline calcium levels. Adverse effects of cinacalcet included nausea, vomiting, and headache.
Parathyroid glands are endocrine organs located behind the thyroid gland in the neck. They are necessary for proper bone development, and to control the level of calcium in the blood. The parathyroid glands make parathyroid hormone, which takes calcium from bones so that it will be available in the blood for nerve conduction and muscle contraction.
"This trial is an important milestone for patients suffering from this devastating form of cancer,” said Dolores Shoback, Associate Editor of the Journal of Clinical Endocrinology and Metabolism. “Cinacalcet is the first agent to target the main control switch for parathyroid hormone secretion—the calcium receptor. All prior therapies for this disease work on the bone and patients quickly become refractory to those treatments."
Other researchers working on the study include Drs. Mishaela Rubin and John Bilezikian of Columbia University, Dr. Charles Faiman of the Cleveland Clinic Foundation, Dr. Munro Peacock of the Indiana University School of Medicine, Dr. Dolores Shoback of the Department of Veterans Affairs Medical Center, Dr. Robert Smallridge of the Mayo Clinic College of Medicine, and Drs. Schwanauer, Olson, and Klassen from Amgen, Inc.
JCEM is a publication of The Endocrine Society. Dr. Silverberg’s article “Cinacalcet Hydrochloride Reduces the Serum Calcium Concentration in Inoperable Parathyroid Carcinoma” will appear in the October issue of the journal.
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