Chemotherapy plays a very important role in cancer treatment. However, there are still some barriers in the successful use of such therapies, mainly because of the adverse side effects of the anticancer agents and due to the development of chemoresistance. This paper focuses on the use of ultrasound to enhance chemotherapy and to overcome drug resistance. The action of many anticancer agents can be improved with the use of ultrasonic exposure either in vitro or in vivo. Drug resistance can be circumvented using ultrasound alone. Furthermore, the reversal attributable to chemoresistance modifiers, such as verapamil and PSC 833, is augmented by ultrasound. Ultrasound-mediated chemosensitization is usually achieved via increasing intracellular drug accumulation, although other mechanisms are also involved. Ultrasound also can play a role in targeted chemotherapy, releasing anticancer chemicals directly and efficiently into the lesions. However, this promising modality has not been clinically adopted so far and the reasons are discussed.

Key words: Chemotherapy; Cancer; Ultrasonic therapy; Chemoresistance; Targeted therapy.