AbstractObjective(s)Although photodynamic therapy is considered as a noninvasive method, most photosensitizers are susceptible to ultrasound. Therefore, it is expected that the combination of two activation methods might have a synergistic effect. This probable effect has been investigated in this study.Materials and MethodsThis study was conducted on colon carcinoma tumor in Balb/c mice. The tumors were induced by subcutaneous injection of CT26 cells. Ultrasound and light irradiations were performed on tumors 24 hr after injection of liposomal Zn (II)-phthalocyanine. The treatment efficacy was evaluated using daily measurement of the tumor dimensions. ResultsTen days post treatment, relative tumor volumes of all groups were significantly reduced in comparison with the main control group. The best response was observed when one of the two treatment methods had been applied. The longest doubling time of tumor was related to the treatment group namely photodynamic, sonodynamic and combination technique, while the shortest belonged to the control group.ConclusionThis study showed that liposomal Zn phthalocyanine is both photosensitizer and sonosensitizer. Photodynamic and sonodynamic therapies can be efficient in retarding tumor growth rate. In this study, the combination of two methods didn’t show any improvement in therapeutic outcomes. It is predicted that latest results are related to the treatments sequence and could be optimized in the future.