Prognostic and Predictive Markers in Medullary Thyroid Carcinoma

Abstract

Unlike papillary thyroid carcinoma, medullary thyroid carcinoma is insensitive to adjuvant treatment with radioactive iodine. The clinical management of patients with advanced or metastatic disease remains challenging since no effective systemic adjuvant therapy is available. We aimed to identify markers of aggressive disease and novel drugable protein targets that would provide systemic adjuvant treatment for patients with advanced medullary thyroid carcinoma. We therefore examined morphologic features of aggressive behavior and the expression of 41 proteins involved in apoptosis, cell cycle, angiogenesis, inflammation, cell adhesion, tumor-specific markers, and WNT, SHH, and AKT pathways using tissue microarray from 23 patients with medullary thyroid carcinoma. Protein expression was determined using computerized image analysis software. Statistical analysis was carried out to correlate clinical data with the average score for each marker. Angioinvasion proved to be the most reliable predictor of disease recurrence and death. The rate of angioinvasion was 43%. All angioinvasive medullary thyroid carcinomas had locoregional and/or distant metastasis; 60% of angioinvasive medullary thyroid carcinomas developed distant metastasis. We identified expression of several potentially important protein targets such as COX-1/2, Bcl-2a, Gst-π, Gli-1, Gli-2, Gli-3, and Bmi-1 that may be therapeutically targeted in medullary thyroid carcinoma. More importantly, the immunohistochemical profile of SSTRs in medullary thyroid carcinoma may also have clinical relevance for the administration of peptide receptor radionuclide treatment. Successful outcome of clinical trials directed against these novel targets would provide much needed systemic adjuvant treatment for patients with advanced medullary thyroid carcinoma, and our data suggest the possibility of stratifying patients who are likely to require adjuvant therapy before their burden of disease precludes successful therapeutic effect.