Research team says diagnostic test for medullary thyroid cancer has mixed results

Detecting thyroid cancer is not always easy, and new research has put the efficacy of a common diagnostic test in doubt. A pair of Italian clinicians recently determined that serum calcitonin (CT) measurement may not always be a reliable indicator of the presence of medullary thyroid cancer (MTC).

Published in the journal The Oncologist, the duo's findings indicate that international disagreement over the value of CT measurement may rest on the difficulty in using the test for early diagnosis.

Of the more than 44,000 thyroid cancer diagnoses made every year in the U.S., approximately 2 to 3 percent involve medullary thyroid carcinomas, the National Cancer Institute reports.

The health authority adds that MTC is somewhat more virulent than the papillary and follicular forms of the disease, which account for more than 90 percent of all cases. The five-year survival rate for MTC is 83 percent, compared to 90 and 94 percent for papillary and follicular carcinomas, respectively.

The key to improving survival of MTC is early detection, healthcare experts say. However, the Italian team said that CT measurements can give ambiguous results, making MTC that much harder to screen for.

Medullary cancer affects thyroid cells that produce the amino acid calcitonin, which the body uses to regulate calcium levels and appetite. Blood levels of calcitonin above 100 picograms per milliliter may indicate medullary carcinoma, according to the American Thyroid Association.

The problem is that most patients discover that they have MTC after their doctor detects a lump in their thyroid gland, not after CT tests, the Columbia University Department of Surgery states. Hence, the Italian researchers' conclusion that while CT measurement is cost effective and generally accurate, it may not be the most reliable early diagnostic tool.

They added that "selective aggressive case finding" may improve MTC outcomes.