Treatment of Murine Tumor Models of Breast Adenocarcinoma by Continuous Dual-Frequency Ultrasound

Abstract

<strong>Introduction:</strong> Acoustic transient cavitation is the primary mechanism of sonochemical reaction and has potential use for tumor treatment. In this study, the <em>in vivo </em>anti-tumor effect of simultaneous dual-frequency ultrasound at low-level intensity (I_SATA< 6 W/cm²) was investigated in a spontaneous murine model of breast adenocarcinoma in Balb/c mice. <br/><strong>Materials and Methods:</strong> Forty tumor bearing mice were divided into four groups (10 in each group). The treated groups received 15 or 30 minutes of combined dual-frequency ultrasound in continuous mode (1 MHz_con+ 150 kHz_con) respectively. The control and the sham groups contained the untreated mice. The tumor growth delay parameters including tumor volume, relative tumor volume, T₅ and T₂ (the needed time for each tumor to reach 5 and 2 times the initial tumor volume, respectively), survival period and percent of tumor growth inhibition ratio were measured on different days after treatment. <br/><strong>Results:</strong> The results showed that the 30 min treatment was effective in tumor growth delay and percent of tumor growth inhibitory ratio compared to the sham and the control groups. The tumor volume growth and relative volume of tumors in the same treated group showed an anti-tumor effect relative to the sham and the control groups. There was a significant difference in tumor volume growth between this 30 min treatment group and the sham group 12 days after treatment (p-value <0.05). The mean of the survival period for animals in the 30 min treatment group was 16% more than the control group. The percent of tumor growth inhibition in the 30 and 15 min treatment groups were 23% and 20% respectively, showing a statistically significant difference. <br/><strong>Conclusion:</strong> Sonodynamic therapy with combined dual–frequency ultrasound in progressive wave mode can be useful in cancer therapy.