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The U.S. Food and Drug Administration on Friday expanded its approval of Bristol-Myers Squibb Co's immunotherapy drug Opdivo for patients with an additional form of advanced lung cancer.

The agency said Opdivo may now be used in patients with non-squamous non-small cell lung cancer (NSCLC) whose disease has progressed during or after platinum-based chemotherapy.

Opdivo, known chemically as nivolumab, was first approved to treat advanced melanoma, the deadliest form of skin cancer, and later for squamous non-small cell lung cancer.

While the expanded approval was widely expected based on clinical trial data, the FDA announcement came about three months ahead of the agency's mid-January action data.

Lung cancer has a far larger patient population than melanoma, with NSCLC accounting for up to 90 percent of all cases, and is seen as a more lucrative use for the new medicines like Opdivo that help the immune system fight the disease.

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Lung cancer is the leading cause of cancer death in the United States, with an estimated 221,200 new diagnoses and 158,040 deaths in 2015, the FDA said.

The squamous cell variety accounts about 25 percent to 30 percent of NSCLC cases, with non-squamous accounting for about 45 percent to 60 percent. Squamous and non-squamous refers to the type of cells in which the cancer occurs, and they tend to be situated in different parts of the lung.

Opdivo competes with an immunotherapy drug from Merck & Co called Keytruda. Bristol recently began a high-profile direct-to-consumer ad campaign for Opdivo in lung cancer, with commercials running on prime-time network television shows.

Bristol-Myers shares were up 58 cents, or about 1 percent, at $61.09 on the New York Stock Exchange.