Laser immunotherapy in treatment of metastatic prostate tumors in rats

Laser immunotherapy is a special cancer treatment modality using an intratumor injection of a special formulation consisting of a novel immunoadjuvant and a laser-absorbing dye, followed by a non-invasive near-IR laser irradiation. Our early experiments using a metastatic mammary rat tumor model showed that laser immunotherapy could cause acute selective photothermal tumor destruction and induce a systemic, long-term specific anti-tumor immunity. In the current study, laser immunotherapy was used to treat metastatic prostate tumors in Copenhagen male rats. The transplantable tumors metastasize mainly to the lung and the lung cancer is usually the cause of death. Two experimental were performed in our study. The first was to study the effect of laser immunotherapy on the tumor burdens, both the primary and the metastasis in the lung. The second was to study the effect of laser immunotherapy on the long-term survival of the tumor-bearing rats. For comparison, some rat tumors were also treated by the laser-dye combination to study the photothermal effect. Tour results showed that both the photothermal effect and the laser immunotherapy could slow the growth of primary tumors and the metastatic tumors. The laser-dye-immunoadjuvant treatment resulted in more than 20 percent long-term survival rate in tumor-bearing rats. Our experimental results indicate that the laser immunotherapy has a great potential in treating metastatic tumors.