Methods of modulating cell-adhesion mediated drug resistance

A method for inhibiting cell adhesion mediated drug resistance wherein an effective amount of a bisphosphonate compound or a pharmaceutically acceptable bisphosphonate salt is administered to a patient having cancer, whereby the efficacy of chemotherapy or radiotherapy directed against the cancer is enhanced. Preferably, the bisphosphonate compound is etidronate, clodronate, pamidronate, or zoledronate. The bisphosphonate compound is preferably administered to the patient prior to the administration of chemotherapy or radiation therapy. Inhibition of cell adhesion mediated drug resistance (CAM-DR) by bisphosphonate in multiple myeloma cells is disclosed.