By Kristina Rebelo
SAN DIEGO -- October 9, 2009 -- Further investigation is recommended in the hunt for thyroid malignancy in patients presenting with a thyroid mass with a ratio of thyroglobulin to serum thyrotropin <=2.6, according to research presented here on October 4 at the American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNSF) Annual Meeting 2009.
The link between thyroid stimulating hormone and well-differentiated thyroid cancer (WDTC), one of the most curable of all neoplasms when surgically resected, is well established. Postoperative evaluation was aided by thyroglobulin; however, this large retrospective study found that the thyroglobulin to serum thyrotropin ratio could be used as a supplemental marker for WDTC.
"Benign thyroid disease is a common finding, but incidence of thyroid malignancy is rapidly increasing because of increased detection," said Michael N. Pakdaman, MD, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts.
Because benign thyroid disease is so common, the study sought to determine how benign disease could be differentiated from malignant disease. Fine-needle biopsy is the gold standard in determining a patient need for surgery, but indeterminate or nondiagnostic results often make that determination difficult. Therefore, this retrospective study investigated several biomarkers that may help in clinical decision making for surgery.
The researchers looked at 1,047 patients who had undergone total thyroidectomy at McGill University, Montreal, Quebec, and comprised a database that had been created by Dr. Pakdaman. The analysis included the 285 patients who had thyroglobulin and serum thyrotropin measured preoperatively.
The thyroglobulin-thyrotropin ratio ranged from 0.095 to 215,000 and, on pathological analysis of thyroid nodules, was correlated to the incidence of malignancy (68%) and occurrence of papillary and micropapillary thyroid cancer.
Dr. Pakdaman said the incidence of thyroid disease has risen in recent years by about 25%, but the death rate has remained unchanged. He suggested that potential factors include radiation exposure; changes in diet with resulting obesity, leading to increased evaluation for thyroid disease; and, most significantly, an increase in detection of existing thyroid cancer as a result of improved ultrasound techniques and technology.
"The bottom line is that we are finding smaller tumours that we could not find before because we did not have the technology," said Dr. Pakdaman.
The study was limited because of its retrospective nature.
"Unfortunately, much of the thyroid research is retrospective, but it does shed light on the disease," said Dr. Pakdaman, who added that his research group will continue to build on their database and prospectively follow patients with other thyroid biomarkers. They will also begin to collect data on thyroglobulin antibodies.
The researchers recommended additional investigation into the clinical use of the thyroglobulin to serum thyrotropin ratio.
[Presentation title: Tg TSH Ratio as a Tumor Marker for Thyroid Cancer. Abstract SP196]
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