18F flouropaclitaxel (FPAC) distribution in malignant tumors is expected to be similar to that of paclitaxel. It is proposed that by monitoring the influx and efflux of FPAC in vivo using PET imaging, we will be able to determine if a tumor retains the drug (is drug sensitive) or pumps it out (is drug resistant). The efflux rate of FPAC in the tumor should be proportional the amount of Pgp present and therefore should be a predictor of treatment failure. If this method is successful at identifying MDR, patients can be spared a course of ineffective chemotherapy and can be started on alternative drugs or, if available, an effective MDR modulator can be administered prior to treatment.