Combination sonodynamic therapy with immunoadjuvant may be a promising new modality for cancer treatment

Sonodynamic therapy (SDT) is a new cancer therapy basing on photodynamic therapy (PDT). Some chemicals produce free radicals on irradiation with laser (photosensitizers) or ultrasound (sonosensitizers). These active molecules destroy biological tissues, thus producing therapeutic effects. Although PDT has been adopted in clinical cancer therapy especially for superficial cancers, this modality is under continued investigation for improved efficacy and expanded use. For example, PDT-generated tumor cell lysates are effective cancer vaccines; treatment of PDT in conjunction with immunoadjuvant, called "PDT-immunoadjuvant therapy" (PIT), "photoimmunotherapy" or "laser immunotherapy", is considered to be a promising therapeutic interventions for the treatment of cancers. Ultrasound, especially focused ultrasound, can penetrate deeply into tissues and can be focused into a small region of a tumor to activate the cytotoxicity of sonosensitizers. This is a unique advantage in the non-invasive treatment of nonsuperficial tumors when compared to laser light used for PDT. For the similar mechanism of PDT and SDT, we hypothesize that SDT may be exploited for the generation of effective therapeutic cancer vaccines like PDT; and combination SDT with Immunoadjuvant may be a promising systemic treatment modality, not only for superficial cancers but also for deep-seated tumors, which would surpass PIT.