No treatment exists for medullary thyroid carcinoma (MTC) once it has spread to the lungs, liver or other distant sites. But a phase II clinical trial of Vandetanib — an oral, targeted therapy — has shown promise, according to research conducted at Washington University School of Medicine and elsewhere. Results were published February in the Journal of Clinical Oncology.
“This is the first clinical trial of a compound that has shown any significant effect in medullary thyroid cancer,” says study co-author Jeffrey Moley, MD, chief of the Division of Endocrine and Oncology Surgery and associate director of the Siteman Cancer Center.
MTC accounts for about 10 percent of all thyroid cancers. For years, the Siteman Cancer Center has played a pioneering role in the diagnosis and treatment of the disease. In 1993, a team led by Washington University surgeon Samuel Wells, MD, identified the MEN2A gene, which is responsible for an inherited form of MTC. The team, which also included Moley and Paul Goodfellow, PhD, discovered that abnormalities in a gene called RET are associated with MEN2 tumors. The team then developed a genetic test for MEN2A. Those who tested positive — meaning they have a 100 percent chance of developing cancer—could have surgery to remove the thyroid gland.
Surgery is still the only effective treatment for localized MTC, but not all patients are diagnosed before the disease spreads. Vandetanib is an investigational drug that blocks factors that feed tumor growth and the enzyme RET kinase, produced by the RET gene.
In the trial, 30 patients with locally advanced or metastatic hereditary MTC received 300 mg of Vandetanib daily. The therapy reduced tumor size or stabilized tumor growth in 73 percent of patients. The length of time from the start of treatment until tumors started growing again was 27 months. For the six patients whose tumors shrank while taking the therapy, the median duration of response was 10 months. The most common side effects of the medication were diarrhea, rash, fatigue and nausea.
Vandetanib is also being evaluated in the treatment of lung and prostate tumors. Wells, SA, et al. Vandetanib for the Treatment of Patients With Locally Advanced or Metastatic Hereditary Medullary Thyroid Cancer. Journal of Clinical Oncology, vol. 28:5, pp. 767-772. February 2010.