Therapeutic Difficulties in Poorly Differentiated and Undifferentiated Thyroid Cancer

Abstract

Poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) have poor prognosis and rare incidence compared to well differentiate thyroid cancer. Since the original description of PDTC in 1983, PDTC was introduced as a separate entity in the 2004 WHO Classification of Endocrine Tumors. PDTC was defined as a thyroid cancer with thyroglobulin-producing non-follicular non-papillary growth pattern and high-grade features, having an intermediate behavior between well differentiated thyroid cancer (WDTC) and ATC. But the criteria of PDTC are still controversial and heterogeneously applied in the diagnostic practice. Also the modalities of treatment, such as the extent of thyroid surgery, the use of radioiodine therapy and external radiation therapy are still controversial. ATC is rapidly progressing human carcinoma with a median survival of 4 to 12 months after diagnosis. Although the complete resection combined with external radiation therapy was reported to be effective recently and multimodality treatment has been recommended, current treatment of ATC has not been adequate for controlling the diseases. Therefore there are new attempts for treatment, such as chemotherapy with paclitaxel, clinical trials of combretastatin 4 phosphate and CS-7107 and multitargeted therapy of bevacizumab with doxorubicin, sorafenib, sunitinib etc. PDTC and ATC are an unexplored field like this, therefore, the studies for molecular pathology and therapeutic approach are necessary for improving survival and quality of life of patients.