Gene-expression Classifier in Papillary Thyroid Carcinoma: Validation and Application of a Classifier for Prognostication

Background: No reliable biomarker for metastatic potential in the risk stratification of papillary thyroid carcinoma exists. We aimed to develop a gene-expression classifier for metastatic potential. Materials and Methods: Genome-wide expression analyses were used. Development cohort: freshly frozen tissue from 38 patients was collected between the years 1986 and 2009. Validation cohort: formalin-fixed paraffin-embedded tissues were collected from 183 consecutively treated patients. Results: A 17-gene classifier was identified based on the expression values in patients with and without metastasis in the development cohort. The 17-gene classifier for regional/distant metastasis identified was tested against the clinical status in the validation cohort. Sensitivity for detection of metastases was 51.5% and specificity 61.6%. Log-rank testing failed to identify any significance (p=0.32) regarding the classifier's usefulness as a prognostic marker for recurrence. Conclusion: A 17-gene classifier for metastatic potential was developed, and the results showed a clear biological difference between groups. However, through validation, no prognostic significance of this classifier was shown.