Extracorporeal shock waves: perspectives in malignant tumor treatment

Progress in basic research led to the design of new generations of anticancer drugs with some notable achievements. Over the years, more and more powerful drugs have been developed with the purpose of increasing the rate of response to therapy. As molecular power of chemotherapeutic agents increased, unfortunately also toxicity and undesired side-effects increased. The search for new therapeutic strategies to be used in the management of cancer is one of the more promising strategies to reduce chemotherapy toxicity. Extracorporeal Shock Waves (ESW), widely used for the treatment of urolithiasis, have been reported to cause modifications of cell growth both in vitro and in vivo. They exert an agonist cytotoxic effect with several chemotherapeutic agents, such as cisplatin, doxorubicin, bleomycin, paclitaxel. Moreover, as it has been reported that their main mechanism of action is an increase in cell membrane permeability, ESW are also used to deliver oligonucleotides and other small particles to cells. Recently, it was found that certain dye compounds, in particular porphyrins, can achieve a cytopathogenic effect when the disease site is subjected to ultrasound irradiation. This technique is referred to as sonodynamic therapy. Based on the new knowledge regarding the interaction between ultrasound with bulk liquid, several studies have shown a synergic effect of ESW and porphyrins in vitro, thus opening a new perspective in sonodynamic therapy, able to overcome some drawbacks encountered during conventional anticancer drug treatment. Finally, current advances in bioengineering encouraged the application of nano-scale technologies to medicine. Nanobubbles, composed of an external shell and a gas core, can deliver chemotropic drugs and porfirins, to target tumour tissues in response to physical triggers, and ESW features make them an ideal alternative to ultrasound in combination with drug-loaded nanobubbles in delivery strategies.