GlaxoSmithKline said the FDA has approved its advanced breast cancer treatment Tykerb (lapatinib).Tykerb is developed for use in combination with Roche’s Xeloda for the treatment of patients with advanced or metastatic breast cancer who haven’t responded to other drugs including Genentech’s Herceptin, which is also marketed by Roche in overseas markets. Tykerb should be available in about two weeks.Approval of Tykerb was granted following a six-month priority review. Analysts expect annual sales of the drug to reach $1 billion by 2010.Treatment with Tykerb will cost around $2,900 a month, Glaxo said in a published report. GlaxoSmithKline said it is also studying the drug for the treatment of earlier-stage breast cancer and head and neck cancers.