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Gene test may reduce unnecessary thyroid surgeries

2 July 2012
Appeared in BioNews 663

A test which screens for levels of gene expression may help reduce the number of patients with benign thyroid cancer who are put forward for unnecessary surgery.

In a study published in the New England Journal of Medicine, the test, developed by US biotechnology firm Veracyte, had 93 percent success in correctly reclassifying samples deemed 'inconclusive' as 'benign'. The test works by analysing the expression patterns of 142 genes and uses 25 supplemental genes to improve classification of rare cancer subtypes.

Enlarged thyroid nodules are often the first symptoms of thyroid cancer, and a biopsy is taken to determine whether the disease is malignant. However, in around 15 to 30 percent of cases results from cytology tests are inconclusive and surgery is usually recommended to remove part or all of the affected tissue. Apart from facing the risk of surgical complications, patients who have had their thyroids removed completely are dependent on life-long hormone supplements.

In a double-blind study conducted over 19 months, biopsy samples were taken from 4,812 patients. Initial cytology analysis indicated 12 percent of the samples could not be classified as either benign or malignant, and surgery was subsequently performed to remove part or all of the thyroid nodule.

Samples were simultaneously tested for gene expression patterns using Veracyte's test, and by histopathology, the gold standard used to determine a definitive diagnosis. The pathologists performing these tests were unaware of the outcome of the gene expression analysis.

Of the 85 samples classified as malignant by histopathology, the gene expression classifier correctly determined 78 as malignant. The classifier also identified 93 of the 180 non-malignant samples. All 55 samples classified as malignant after histology were also confirmed to be malignant by the classifier.

Professor Bryan Haugen, a co-investigator on the study from the University of Colorado, says, 'Our results showed that the gene expression test can substantially reclassify otherwise inconclusive thyroid nodule cytology results'.

Veracyte says that the gene expression classifier can help doctors make valuable treatment decisions, such as deciding between partial and total removal of the thyroid. Patients whose biopsy is considered 'indeterminate' but who receive a negative gene expression classifier result are likely to have a lower risk of developing cancer and may not require immediate surgery.

Bonnie Anderson, the chief executive officer of Veracyte, said: 'This is a key step forward for us. Ultimately, these results should underscore the potential of the genomic test to help physicians make more informed treatment decisions early, thus improving patient care and helping to take significant costs out of the healthcare system'.

According to the most recent figures available from Cancer Research UK, 2,340 cases of thyroid cancer were diagnosed in 2009 and 346 people died of the disease in 2010.

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