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556 MYAKISHEV-REMPEL ET AL. measuring baseline growth rates for each tumor before the beginning of red light therapy, and then comparing the growth rate of each tumor before and after beginning the therapy. Automation and human interventions We have developed a new method that uses a well- characterized animal model for the study of the effects of LLLT on cancer. The advantage of this model is that the setup minimizes the human factor, both in influencing mouse behavior and in data analysis. The mice are irradiated automatically and the tumors are sized across time using image morphometry blinded to treatment, thus excluding human bias. Evidence supporting the safety of red light This study aimed to maximize the healing and activation effects while avoiding the inhibitory effects of red light. We selected the red light dose and fluence very conservatively based on our prior studies on wound healing.13 Treated mice received two irradiations per day at 8mW/cm2 flu- ence for 312 sec per session, resulting in a total dose density of 2.5 J/cm2 per session (5 J/cm2 per day). This regimen is in general agreement with the one used by Erdle et al.14 Erdle et al. used the same red light source and mouse strain (SKH-1), measured incisional wound healing, and demon- strated the high efficiency of chronic daily treatment at a dose of 3.6J/cm2 (either 450sec at 8mW/cm2 or 37min at 1.6 mW/cm2). This study documented the absence of strong positive or negative effects of LLLT on tumor growth in this model and red light treatment parameters. Prior studies using the same red LLLT system demonstrated that these parameters stim- ulate wound healing.13 The present study provides some evidence that phototherapy at these parameters should not be empirically contraindicated in the treatment of patients with cancer. Our qualitative observations of improvement in skin quality at early time points, and relief of sickness be- havior at later stages of the investigation, are also suggestive of the fact that the light was capable of producing beneficial effects for the whole animal despite the presence of tumors. It should be recognized, however, that the present study de- livers, essentially, whole body therapy to the affected indi- vidual, rather than treating a specific area. The small but statistically significant decrease in tumor area observed on days 16–23 demonstrates the ability of our model to detect small changes in tumor volume because of the low degree of random histotype variability in the model and the high number of examined tumors and time points. An additional explanation as to why red light was beneficial at days 16–23 may be the stimulation of antitumor immune activity or, perhaps, a local photodynamic effect as a result of red light activation of endogenous porphyrins present in tumors in and around areas of spontaneous hemorrhage and necrosis. Red light treatment was qualitatively observed to relieve sickness behavior, which suggests that there was an improved host response and increased antitumor immunity; at least until the tumor burden overwhelmed these effects. Future studies directed at studying these immune effects would be helpful in determining the biological basis for these observations. Targets of the red light Important factors to consider are: what tissues were reached by the red light during whole body phototherapy as was the case in this study, and which chromophores are absorbing the light. Because the mice have hairless fair skin, the light was not shielded by hair or melanin. The necrotic tissue covering some of the tumors might have shielded some tumor cells from the red light and/or may have gen- erated local photodynamic effects caused by interaction with endogenous porphyrins. Much of the light likely did pene- trate deeper in the mouse, potentially stimulating lymphatic vessels, lymph nodes, internal organs such as the spleen, and, possibly, even the bone marrow. It is likely that both actively dividing tumor cells and immune cells including white blood cells; immune cells infiltrating the skin such as mast cells, dendritic cells, neutrophils, and other, lymphatic vessels and nodes; bone marrow; and, possibly, spleen were absorbing and being activated by the light treatments. As this study suggests that the outcome of red light therapy depends upon competition between possible acti- vation of tumor growth on the one hand, and improvement of systemic antitumor immune response on the other, future studies should address the issue of local versus systemic red light therapy. Treatment was systemic in this case because of whole-body photoirradiation. Specific studies would be helpful, particularly if treatment can be isolated and directed solely to healthy tissues, both tumor-bearing and healthy tissue, or tumors alone. Conclusions The present study failed to demonstrate a harmful effect of whole-body red LLLT on tumor growth in an experimental model of UV-induced SCC. There was a transient and small reduction in relative tumor area in the treatment group compared with controls. This study suggests that LLLT should not be withheld from cancer patients on an empiric basis. Further investigations designed to build upon these observations and determine the mechanism for the host– tumor responses noted during the early treatment phase are warranted. Acknowledgments This work was performed at The Rochester General Hospital Surgical Laser Research Laboratory and funded in part by Quantum Devices (Barneveld, WI), and the Kidd Fund of the Rochester General Hospital Foundation. Dr. Myakishev-Rempel’s research was supported in part by an NIH T32 AR007472 grant. We thank Drs. Alice Pentland and Francisco Tausk for their support and for sharing the mate- rial resources for these experiments. The LED sources used for this study were provided by Dr. Harry Whelan and the NASA Marshall Space Flight Center. We thank Prof. Lars Hode and Dr. Gerald Ross for their discussion and literature contributions. Author Disclosure Statement Dr. Myakishev-Rempel has been compensated for this work by Warp Photomedicine (Barneveld, WI). No compet- ing financial interests exist for the other authors.PDF Image | Preliminary Study of the Safety of Red Light Phototherapy Cancer
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