Letrozole and Imatinib Mesylate in Treating Postmenopausal Participants With Estrogen or Progesterone Positive Metastatic Breast Cancer

This phase II trial studies the side effects and how well letrozole and imatinib mesylate work in treating postmenopausal participants with estrogen or progesterone positive breast cancer that has spread to other places in the body. Letrozole is an antihormonal drug used in the standard treatment of hormonal sensitive breast cancer. Imatinib mesylate is a drug that binds to certain proteins on the tumor cells and prevents them from further growth. Imatinib mesylate is thought to prevent the potential resistance to letrozole, which may make the letrozole more effective. Giving letrozole and imatinib mesylate may work better in treating participants with breast cancer.