"Removing the tumors completely reverses the condition," says Suzanne M. Jan de Beur, M.D., assistant professor of medicine at Johns Hopkins, "but because they are small, slow-growing and frequently located in unusual sites, conventional imaging techniques often fail to detect them."
Now Jan de Beur and colleagues have found a way to smoke out most tumors from their hiding places. Knowing that the tumors express the receptor for the hormone somatostatin, they injected patients with a radioactive agent called pentetreotide, which binds to the same receptor. After 48 to 72 hours, they used gamma X-rays on each patient, looking for signs of radioactivity. The technique correctly pinpointed the tumors' locations in five of seven patients studied. Results are reported in the March 2 issue of The Lancet.
"Our findings suggest that pentetreotide imaging is a good initial test to assess people with oncogenic osteomalacia, and also can be used as a diagnostic screening tool for patients with similar symptoms," Jan de Beur says.
Oncogenic osteomalacia disrupts metabolism when the tiny tumors secrete a chemical that prevents kidneys from absorbing phosphate, a major component of bones. There are only 100 or so cases reported in the medical literature, but Jan de Beur thinks it's underdiagnosed. She has seen nine patients in the past four or five years. Too often, she says, the condition is missed or mistaken for arthritis, bone cancer or even emotional stress. Patients are left to endure pain that could have been prevented.
In the study, pentetreotide imaging identified tumors in such varied places as the sinus cavity, the groin and the arm. One patient plagued with bone fractures for years was found to have a tumor between the thumb and forefinger of his left hand. It was removed in an outpatient procedure and he felt better within weeks.
The study was supported by the National Institutes of Health. Other authors were Elizabeth A. Streeten, A. Cahid Civelak, Edward F. McCarthy, Lillana Uribe, Stephen J. Marx, Olufunmilayo Onobrakpeya, Lawrence G. Raisz, Nelson B. Watts, Michael Sharon and Michael A. Levine.
Jan de Beur, S.M. et. al., "Localisation of mesenchymal tumours by somatostatin receptor imaging," Lancet, March 2, 2002, Vol. 358.
Related Web sites:
Johns Hopkins Division of Endocrinology and Metabolism
http://www.endocrinology.jhu.edu
Division of Pediatric Endocrinology at Johns Hopkins http://www.hopkinsmedicine.org/pediatricendocrinology
Article from Johns Hopkins Internist newsletter http://www.med.jhu.edu/deptmed/Internist/may01/osteomalacia.html
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Journal
The Lancet