The Food and Drug Administration on Wednesday approved a new use for ImClone Systems' ( IMCL) Erbitux, endorsing the drug as a treatment for head and neck cancers. "This is the first drug approved for head and neck cancer that has shown a survival benefit in this population," the FDA said. Erbitux is the first drug approved to treat head and neck cancer since methotrexate became available in the 1950s, the FDA said. Erbitux, initially approved for treating colorectal cancer, received the agency's clearance as a treatment -- in combination with radiation -- for head and neck cancers that can't be removed by surgery. The FDA also approved Erbitux as a single therapy in patients whose head and neck cancers had spread despite traditional chemotherapy. "We consider this approval an important advance in the treatment of head and neck cancer because it has been shown to help some patients live longer," said Dr. Steven Galson, director of FDA's Center for Drug Evaluation and Research. Bristol-Myers Squibb ( BMY) is Erbitux's marketing partner in North America. The German drug and chemical company Merck KGaA handles the marketing in Europe. Last week, Merck said it received a favorable opinion from a European Union scientific advisory panel about Erbitux as a head and neck cancer treatment. The FDA's announcement Wednesday came after the markets had closed. In regular trading, ImClone gained 61 cents, or 1.6%, to $39. After hours, the stock lost $1.05. Also, in the regular session, Bristol-Myers Squibb fell 33 cents, or 1.4%, to $22.77. The stock gained 13 cents in extended trading.