Contemporary directions of application of low power ultrasounds in anticancer therapy

Abstract

In the recent years, research has been conducted on the role of ultrasounds (US) in anticancer therapy. Although the mechanisms of impact on cancer cells have not yet been fully understood, it is known that the best results are obtained using low power ultrasound. Currently applying ultrasounds to organisms is considered in three areas of influence: thermal (thermic effect), cavitation (cavitation effect), other than thermal and cavitation ones (non-thermal, non-cavitation effect). Under the influence of ultrasonic wave with low power, the absorption of drugs is increased as well as of anti-angiogenic activity. Sonodynamic therapy is aimed at destroying dividing cancer cells through the formation of free radicals in the cavitation mechanism and in the presence of sonosensitizers. At the same time under the influence of US, local hyperthermia is generated. In vivo studies showed a synergistic increase in cytotoxicity due to the effects of ultrasonic hyperthermia and adriamycin. The thermal effect and inertial cavitation are described as two factors induced by US, which may lead to damage to the vascular network within the neoplastic lesion. A proportional increase in tumor echogenicity to the frequency range of the applied ultrasound wave has been demonstrated. The strategy of combining US with photosensitizers, chemotherapeutics or contrast agents is gaining more and more recognition. Obtained results from inter developed studies on antineoplastic sonodynamic therapy indicate that it may become a new additional cancer treatment strategy.