Blood Levels of Genetic Material Predict Thyroid Cancer Recurrence

Scientists at the University of Sydney (NSW, Australia) recruited two groups retrospectively for the comparison of tissue miRNA expression in papillary thyroid cancer (PTC) with and without recurrence: patients with PTC who were diagnosed with recurrence after initial curative treatment and patients with PTC confined to the thyroid gland who had not been diagnosed with recurrence at their latest follow-up. Two additional groups were recruited prospectively for measurements of plasma miRNA levels: patients who had PTC without lateral lymph node or distant metastasis and were undergoing total thyroidectomy and patients who had multinodular goiter and were undergoing total thyroidectomy.

Total RNA was extracted from formalin-fixed, paraffin-embedded (FFPE) samples using the FFPE RNeasy Kit (Qiagen; Hilden, Germany). RNA samples were labeled with fluorescence Hy3 using the miRCURY Hy3/Hy5 power labeling kit and miRNA microarray profiling was performed on the miRCURY Locked Nucleic Acid (LNA) microRNA Array (Exiqon A/S; Vedbaek, Denmark). The expression levels of individual miRNAs were measured with quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) using TaqMan miRNA assays (Applied Biosystems; Foster City, CA, USA).

The investigators found that high levels of two specific miRNAs, miRNA-222 and miRNA-146b, within tumors indicated that cancer was more likely to recur after patients' tumors were surgically removed. The same two miRNAs were present at high levels in the blood of thyroid cancer patients compared with healthy individuals, but after thyroid surgery, the blood levels in the patients fell to normal levels.

The current blood test for the detection of recurrent papillary thyroid cancer is not accurate in up to a quarter of patients either because of interference from the patients' antibodies or other cancer-related factors. James Lee, MBBS, FRACS, the lead author of the study, said, “Our results suggest that we may be able to track the presence of papillary thyroid cancer by a microRNA blood test. An alternative blood test measuring microRNA levels would be a great complement to what is already available.” The study was published on October 28, 2013, in the journal Cancer. 

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University of Sydney 
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Exiqon A/S