Photosensitizer-enhanced
laser treatment, where
dyes are activated in situ by
lasers of appropriate wavelengths, provides highly selective tissue destruction, both spatially and temporally, through photophysical reactions. Although
laser-sensitizer treatment for
cancer can achieve a controlled local
tumor cell destruction on a large scale, total
tumor eradication may not be accomplished because of the incomplete local
tumor killing or the presence of
tumor metastases, or both. The long-term control of
cancer depends on the host immune surveillance and defense systems in which both cell-mediated and humoral responses are critical. In this study we report a novel minimally invasive
cancer treatment combining the
laser photophysical effects with the photobiological effects. Irradiation of a rat mammary
tumor by an 805 nm
diode laser, after an intratumor administration of a specific
photosensitizer,
indocyanine green in a
glycated chitosan gel, caused immediate photothermal destruction of neoplastic cells. Concomitantly this treatment stimulated the immunological defense system against residual and metastatic
tumor cells. Increases in survival rate and in the eradication of
tumor burden, both primary and metastatic, were observed after this treatment. Furthermore, the resistance of successfully treated rats to
tumor rechallenge demonstrated a long-lasting systemic effect of the treatment. These findings indicate that our treatment has triggered a specific humoral immune response in the
tumor-bearing rats.