Abstract
Medullary thyroid cancers (MTCs) constitute between 2 and 5% of all thyroid cancers. The 10-year overall survival (OS) rate of patients with localized disease is around 95% while that of patients with regional stage disease is about 75%. Only 20% of patients with distant metastases at diagnosis survive 10 years which is significantly lower than for differentiated thyroid cancers. Cases with regional metastases at presentation have high recurrence rates. Adjuvant external radiation confers local control but not improved OS. The management of residual, recurrent, or metastatic disease till a few years ago was re-surgery with local measures such as radiation. Chemotherapy was used with marginal benefit. The development of targeted therapy has brought in a major advantage in management of such patients. Two drugs—vandetanib and cabozantinib—have been approved for use in progressive or metastatic MTC. In addition, several drugs acting on other steps of the molecular pathway are being investigated with promising results. Targeted radionuclide therapy also provides an effective treatment option with good quality of life. This review covers the rationale of targeted therapy for MTC, present treatment options, drugs and methods under investigation, as well as an outline of the adverse effects and their management.
Highlights
Medullary thyroid cancer (MTC) which arises from parafollicular cells is less common than differentiated thyroid cancer (DTC) constituting between 2 [1] and 5% [2] of all thyroid malignancies. 13–15% of patients of Medullary thyroid cancers (MTCs) present with distant metastasis (DM) and have a 10-year survival of approximately 20% [3, 4]
In a phase II trial of lenvantinib, there was no difference in treatment response according to rearranged during transfection (RET) mutation status; high baseline levels of vascular endothelial growth factor (VEGF) correlated with greater tumor shrinkage, and low levels of ANG2, sTie-2, HGF, and interleukin (IL)-8 were associated with tumor shrinkage and prolonged progression-free survival (PFS) [75]
This distinction is important as the main serious adverse events (AE) associated with the current RET tyrosine kinase inhibitors (TKIs) are related to anti-VEGFR or anti-Epidermal growth factor receptor (EGFR) effects
Summary
The 10-year overall survival (OS) rate of patients with localized disease is around 95% while that of patients with regional stage disease is about 75%. 20% of patients with distant metastases at diagnosis survive 10 years which is significantly lower than for differentiated thyroid cancers. Cases with regional metastases at presentation have high recurrence rates. The management of residual, recurrent, or metastatic disease till a few years ago was re-surgery with local measures such as radiation. The development of targeted therapy has brought in a major advantage in management of such patients. Targeted radionuclide therapy provides an effective treatment option with good quality of life. This review covers the rationale of targeted therapy for MTC, present treatment options, drugs and methods under investigation, as well as an outline of the adverse effects and their management
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