This invention is directed to methods of treating solid tumor cancers, particularly refractory cancers by administration of a drug capable of inhibiting mTOR and/or inhibiting an efflux pump and/or inhibiting HIF-1α and VEGF, the drug in particular being selected from the group consisting of sirolimus, everolimus, zotarolimus, tacrolimus, iolimus A9, deforolimus, AP23572, tacrolimus, temsirolimus, pimecrolimus, novolimus, 40-O-(3-hydroxypropyl), 40-O-[2-(2-hydroxy)ethoxy]ethyl-rapamycin and 40-O-tetrazolylrapamycin, the drug being administered along with a chemotherapeutic agent and/or radiation therapy.