This randomized phase III trial studies how well gemcitabine hydrochloride and docetaxel followed by doxorubicin hydrochloride work compared to observation in treating patients with high-risk uterine leiomyosarcoma previously removed by surgery. Drugs used in chemotherapy, such as gemcitabine hydrochloride, docetaxel, and doxorubicin hydrochloride, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. It is not yet known whether combination therapy after surgery is an effective treatment for uterine leiomyosarcoma.