Site-specific (targeted) drug delivery in cancer therapy

The current status of efforts to target cytotoxic agents to tumor cells using antitumor antibodies and particulate drug carriers such as liposomes and microspheres is reviewed. Emphasis is given to the role of anatomic and physiologic factors in determining the disposition, fate, and therapeutic efficacy of targeted drug delivery systems and to the importance of tumor cell heterogeneity as a major obstacle to effective cancer therapy.