(Reuters) - The U.S. Food and Drug Administration said it approved Japan's Eisai Co Ltd's drug to treat the most common form of thyroid cancer more than two months ahead of the review date.

The drug, Lenvima, was cleared for use in patients with progressive, differentiated thyroid cancer (DTC) who have not adequately responded to radioactive iodine therapy, the agency said on Friday. (http://1.usa.gov/1vIeI1Q)

DTC is a cancerous growth of the thyroid gland, which is located in the neck, and helps regulate metabolism.

Lenvima, known chemically as lenvatinib, is a kinase inhibitor that blocks certain proteins from helping cancer cells grow and divide. The drug is also being tested for use in a plethora of other cancers.

The drug, which was granted "orphan drug status" by the U.S. regulator, was evaluated by the agency under its priority review program. This process expedites review of drugs that, if approved, would provide significant improvement in the treatment of a serious condition.

The FDA was slated to make a decision on Lenvima by April 14.

The approval is backed by data that showed Lenvima-treated patients lived a median of 18.3 months without their disease progressing, compared to a median of 3.6 months for patients who received a placebo.

Lenvima will be sold in the United States by Woodcliff Lake, New Jersey-based Eisai Inc, a unit of Tokyo-based Eisai.

Last year, about 62,980 Americans were diagnosed with thyroid cancer, and at least 1,890 succumbed to the disease, according to the National Cancer Institute.

(This version of the story corrects day to Friday from Thursday in paragraph 2)

(Reporting by Natalie Grover in Bengaluru; Editing by Savio D'Souza and Saumyadeb Chakrabarty)