Findings from the SELECT phase III study show that lenvatinib is highly effective against differentiated thyroid cancer that is resistant to standard radioiodine (RAI) therapy.

The new oral targeted drug delayed disease progression by 14.7 months, and nearly two thirds of patients experienced tumour shrinkage.

The median overall survival had not been reached.

“We are confident that, based on our findings, lenvatinib will eventually become a standard treatment for radioiodine-resistant thyroid cancer,” said lead study author Martin Schlumberger, MD, a professor of oncology at the University Paris Sud in Paris, France.

“As little as a year ago, this group of patients had no effective treatment options. It’s remarkable that we now have two active drugs in this setting, both of them tyrosine kinase inhibitors.”

Differentiated thyroid cancer is the most common subtype of thyroid cancer, accounting for about 85 percent of the 60,000 thyroid cancer cases diagnosed each year in the United States.

Although differentiated thyroid cancer is generally curable with standard treatment – surgery and RAI – roughly 5-15 percent of patients develop RAI resistance.

Another targeted drug called sorafenib was approved by the FDA in November 2013 to treat this same population of patients.

Lenvatinib is an oral tyrosine kinase inhibitor that blocks several targets in a cancer cell,including VEGFR1-3, FGFR 1-4, PDGFR-β, KIT, and RET.

It is being explored in phase II and phase III clinical trials as a potential treatment for liver, lung, and kidney cancers and other types of solid tumours.

In this study, 392 patients with advanced, RAI-resistant, differentiated thyroid cancer that had progressed within a year were randomly assigned to treatment with either lenvatinib or placebo.

Patients on the placebo arm were allowed to cross over to the lenvatinib arm upon disease progression.

Approximately 65 percent of patients experienced tumour shrinkage in the lenvatinib arm, compared to only 3 percent in the placebo arm.

The majority of responses occurred within two months of starting treatment.

The median progression-free survival was 18.3 months in the lenvatinib arm vs. 3.6 months in the placebo arm.

The median overall survival has not been reached.

The five most common side effects of lenvatinib were high blood pressure, diarrhoea, decreased appetite, decreased weight, and nausea.

Although the side effects necessitated dose reductions in 78.5 percent of patients, the benefit of lenvatinib persisted with decreased dose, Dr. Schlumberger noted. 

"This new drug is extremely efficient, and though toxicities were considerable they can be managed with dose modification".

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Source: ASCO