Witnessing a New Era?—The Emerging Role of Targeted Drugs in the Medical Treatment of Advanced Medullary and Anaplastic Thyroid Cancer

Abstract

The treatment of advanced thyroid cancer is currently entering a new era due to the introduction of targeted therapy into modern cancer treatment. The growing insight into the molecular biology of thyroid cancer and on the development of numerous mainly multitargeted agents provide the basis for new treatment strategies. In particular, activation of mitogenic and angiogenic signaling pathways are suitable targets as preclinical and clinical data suggest. Several Phase II and a few Phase III studies were launched in thyroid cancer which included medullary thyroid cancer (MTC) and anaplastic thyroid cancer (ATC) but only a few focused specifically on theses subtypes. A number of smaller Phase II trials reported promising response rates and progression-free survival. Results from a randomized Phase III trial in MTC with vandetanib, a combined vascular endothelial growth factor receptor 2 + 3 (VEGF-R2+3) and RET multi tyrosine kinase inhibitor demonstrated significant clinical activity and resulted in the first approval of a kinase inhibitor for the treatment of MTC in 2011. Unlike in MTC, in ATC the prognosis is dismal due to the aggressive nature of the disease. Some mainly vascular targeting agents alone or in combination with chemotherapy have shown interesting activity in this disease and have raised new hope. Particularly the combination of fosbretabulin with a chemotherapy backbone of paclitaxel and carboplatin tripled the one-year survival rate in a recent Phase II trial which included 80 patients with ATC. In this review, we provide a brief overview of the general treatment concept of MTC and ATC and summarize the compiled evidence published on targeted agents in these rare thyroid cancer subtypes.