Biophysical modes of action of ultrasound are classified as thermal and non-thermal effects. Non-thermal effects of ultrasound include cavitational and non-cavitational effects. The thermal effects of ultrasound have already been used for hyperthermic cancer therapy as well as microwaves and radiofrequency heating. Recently among the non-thermal effects of ultrasound, acoustic cavitation is considered to have the highest potential for therapeutic applications. Many examples of therapeutic applications for which cavitation may be involved have been reported, including sonodynamic therapy, gene therapy, thrombolysis and the use of microbubbles for enhancing ultrasonic action. This subject is of interest because it is related to the development of novel therapeutic applications using ultrasound. The role of cavitational effects in the therapeutic use of ultrasound is reviewed.

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Hyperthermia (HT) has been recognized as an effective and attractive tool in anticancer therapy. However, the results obtained in therapy by HT alone have been only partially satisfactory. Consequently, attention has focused on the search for substances able to sensitize tumor cells to the damage caused by HT without reducing the capacity of normal cells. It has been reported that the tumor cell death in HT is mediated by apoptosis. Activation of a preprogrammed cascade of molecular events will result in DNA degradation and nuclear fragmentation, leading to apoptosis. However, the pathways which can induce apoptosis varies in different cells. If we could discover common stimuli which could induce apoptosis in all types of cells, we would obtain a new anticancer therapy against all types of tumor cells. In this report, we overviewed both mechanisms of HT-induced apotosis, and the substances used to enhance HT-induced apoptosis. Moreover, we provide evidence for the role of intracellular Ca²⁺concentration in HT-induced apoptosis.

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We previously reported that whole-body hyperthermia (WBH) induced by far-infrared ray (FIR) was a beneficial method of WBH, and the merits of glucose administration in combination with hyperthermia have been suggested. Based on this information, the effects of a single trial of WBH alone or in combination with glucose on the growth of spontaneous mammary tumours in mice were studied. While a single intraperitoneal injection of glucose (6 mg/g body weight) had no effect, WBH (for 3 hours, 39-41°C body temperature of mice) alone and glucose injection 30 min before WBH significantly inhibited the tumour growth. Notably, the combined treatment with glucose and WBH suppressed the tumour growth almost completely for 7 days. No deleterious side-effects on body weight change, plasma component levels, major organ weights or external appearance were observed. Thus, the proposed WBH system is promising as a safe, simple and efficient method for the therapy of breast and other types of tumours.

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To evaluate the protective role of whole-body hyperthermia (WBH) and the irradiation with far-infrared ray (FIR) in mammary tumourigenesis, SHN virgin mice were divided into 4 groups at 2 months of age; the first or the second group was placed on the normal or FIR rack (26-27°C) (control or FIR group). The third group kept on the normal rack received WBH (37-42°C) for 3 hours every other day, for 2 months (WBH group) and the fourth group was placed on the FIR rack and given WBH (WBH+FIR group). WBH and FIR inhibited both the development and the growth of spontaneous mammary tumours; the effect on development was much more marked with FIR than WBH, but the opposite was the case for growth. The inhibition was not enhanced in the WBH+FIR group. Body weight was smaller in the WBH and FIR groups, associated with a lower food intake. No deleterious side- or after-effects were observed in organ weight, normal and preneoplastic mammary glands and plasma and urine component levels, or in external appearance. WBH and FIR are promising health-maintaining as well as an antitumour agents.

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