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Thermal therapy has been used for cancer treatment for more than a century. While thermal effect can be
direct, immediate, and controllable, it is not sufficient to completely eradicate tumors, particularly when
tumors have metastasized locally or to the distant sites. Metastases are the major cause of treatment failure
and cancer deaths. Current available therapies, such as surgery, radiation, and chemotherapy, only have
limited curative effects in patients with late-stage, metastatic cancers. Immunotherapy has been considered
as the ultimate approach for cancer treatment since a systemic, anti-tumor, immunological response can be
induced. Using the combination of photothermal therapy and immunotherapy, laser immunotherapy (LIT),a novel immunotherapy modality for late-stage cancer treatment, has been developed. LIT has shown great
promise in pre-clinical studies and clinical breast cancer and melanoma pilot trials. However, the skin
color and the depth of the tumor have been challenges for effective treatment with LIT. To induce a
thermal destruction zone of appropriate size without causing thermal damage on the skin, we have developed
interstitial laser immunotherapy (ILIT) using a cylindrical diffuser. To determine the effectiveness of ILIT,
we treated the DMBA-4 metastatic tumors in rats. The thermal damage in tumor tissue was studied using
TTC immersion and hematoxolin and eosin (H & E) staining. Also observed was the overall survival of the
treated animals. Our results demonstrated that the ILIT could impact a much larger tumor area, and it
significantly reduced the surface damage compared with the early version of non-invasive LIT. The
survival data also indicate that ILIT has the potential to become an effective tool for the treatment of deeper,
larger, and metastatic tumors, with reduced side effects.
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