Long-Term Effect on EMT6 Tumors in Mice Induced by Combination of Laser Immunotherapy and Surgery

Laser immunotherapy (LI) has been demonstrated to be a promising modality for cancer treatment. The present study was designed to further investigate the impact of LI combined with surgery. LI consists of a near-infrared laser, a light-absorbing dye (indocyanine green, ICG), and an immunostimulant (glycated chitosan, GC). ICG and GC were intratumorally injected, followed by laser irradiation. Female BALB/c mice bearing EMT6 tumor cells were divided into 4 groups: control, LI, LI followed by immediate surgery resection of residual tumor (LI + S0wk), and LI followed by surgical removal of residual tumor after 1 week (LI + S1wk). Successfully treated mice from all treatment groups were rechallenged twice with 105 and 5 × 105 EMT6 cells, respectively. The LI + S1wk group had the highest survival rate (72%) after 90 days, whereas the mice survival rates of the LI + S0wk, LI, and control groups were 50%, 46%, 0%, respectively. The median survival times of control, LI, LI + S0wk, and LI + S1wk groups were 32, 66, 74, and 90 days, respectively. Survival rates of the treated mice after the first and second tumor rechallenges, ranging from 73% to 95%, were not significantly different among the 4 groups (P > .05). The results show that LI is a useful tool for the treatment of tumor-bearing mice. Long-term antitumor effect can be induced by LI. They also indicate that combination of LI with surgery can further improve the therapeutic efficiency of LI.