Metastatic Thyroid Cancer
Metastatic thyroid cancer is not very common. Distant spread most commonly occurs in the lungs and bones.
For many years the only treatment option was radioactive iodine (I 131). Chemotherapy has not been very effective in stage IV thyroid cancer.
In recent years a new class of drugs called tyrosine kinase inhibitors have shown efficacy and improvement in survival.
In 2014, sorafenib (nexavar) was FDA-approved for metastatic thyroid cancer (follicular or papillary) not responsive to radioactive iodine. Sorafenib is an oral drug that inhibits the activity of VEGFR (vascular endothelial growth factor) and B-RAF proteins, which contribute to cancer growth. Sorafenib was tested in an international trial that enrolled 417 patients and the results of the trial showed doubling of disease free survival, a large number of patients also had stable disease. The most common side effects were rash, hand foot syndrome, hair thinning and diarrhea.
Another oral drug for metastatic thyroid cancer that showed improved survival is lenvatinib. Lenvatinib was recently FDA approved. Lenvatinib is also a tyrosine kinase inhibitor that works by delaying the growth of thyroid cancer. The trial enrolled 392 patients and showed that progression of their cancer was 18.3 months compared to 3.6 months in the placebo group. The main side effects were diarrhea, HTN, rash, decreased appetite, kidney problems and blood clots.
Other drugs currently in clinical trials for thyroid cancer are axitinib and sorafenib, which are currently FDA approved for renal cell cancer. Due to the small number of metastatic thyroid cancer patients refractory to radio iodine the trials to test new drugs are limited.