it is concluded that hdmtx-lv therapy may be effective in the treatment of osteosarcoma , even when subpopulations of the tumor cells exhibit different mechanisms of resistance to mtx , such as elevated levels of dihydrofolate reductase or a deficient transport system for mtx , if high doses of mtx are applied long enough to ensure lethal intracellular mtx levels and low-dose lv schedules instituted after a long delay are used .
C0029463
osteosarcoma
C0025677
mtx