Adrenocortical cancer (ACC) is a rare tumor that is optimally treated with surgical resection. However, many patients present with unresectable disease and relapses are common after surgical resection creating a need for more effective systemic therapies. Several investigators have reported responses to a variety of chemotherapy agents, without a clear improvement in overall survival. A possible explanation for these disappointing results is the high levels of expression of P-glycoprotein (Pgp) seen in a majority of adrenocortical cancers. Pgp, a membrane protein that can function as a drug efflux pump lowering the intracellular concentrations of various drugs, has been implicated as a mechanism of drug resistance.