The U.S. Food and Drug Administration has approved Amgen Inc.’s denosumab to help reduce fractures in patients whose solid tumor cancers have spread to their bones, expanding the market for an important drug for the company.

For cancer-related uses, the drug will be called Xgeva. The Thousand Oaks biotech already markets the drug under the brand name Prolia for treating osteoporosis in older women, which the FDA approved in June. Now with approval for cancer, the drug is more likely to become a billion-dollar blockbuster.

“Based on the compelling science and robust clinical evidence seen with Xgeva, I expect this new option to quickly become a mainstay of cancer care and to play an important role in reducing the incidence of debilitating bone complications in patients with advanced cancer,” Dr. David H. Henry, a University of Pennsylvania clinical professor of medicine who worked on the drug’s clinical trials, said in an Amgen statement released after the FDA announcement late Thursday.

For cancer-related uses, Xgeva will compete with Zometa, a Novartis AG drug that had sales of $1.47 billion in 2009.

Amgen has been banking on denosumab to boost growth in company revenues, which were significantly hurt after health concerns surfaced about its top-selling anemia drug Aranesp a few years ago. The company’s revenue fell 2.4 percent last year.

Shares were down 38 cents, or less than a percent, to $54.76 in Friday midday trading on the Nasdaq.