A curative treatment strategy using tumor debulking surgery combined with immune checkpoint inhibitors for advanced pediatric solid tumors: An in vivo study using a murine model of osteosarcoma

Background/purpose: This study aimed to assess the significance of tumor debulking surgery by using immune checkpoint inhibitors for advanced pediatric solid tumors in a murine model of advanced osteosarcoma. Methods: In C3H mice, 5 × 10 ⁶ LM8 (osteosarcoma cell line with a high metastatic potential in the lungs originating from the C3H mouse) cells were transplanted subcutaneously. Thereafter, the mice were divided into 4 groups as follows: the control group received no intervention (CG, n = 5), the surgery group underwent subcutaneous tumor resection (tumor debulking surgery) 11 days after transplantation (SG, n = 10), the immunotherapy group received a cocktail consisting of 200 μg each of three antibodies (anti-Tim-3, anti-PD-L1, and anti-OX-86) intraperitoneally on posttransplantation days 11, 14, 18, and 21 (IG, n = 10), and the combination therapy group, tumor debulking surgery on day 11 and the cocktail intraperitoneally on days 11, 14, 18, and 21 (COMBG, n = 10). Survival curves were plotted by using the Kaplan–Meier method and compared with those plotted using the log-rank test. Next, the lungs of mice in the 4 groups were pathologically evaluated. Results: The COMBG showed significantly longer survival than the other three groups (P ≤ 0.002), whereas the SG and IG revealed no difference in survival rate compared to CG. Pathological evaluations revealed no lung metastasis 16 weeks after tumor transplantation in the survivors of COMBG. Conclusions: The results of this study suggest that tumor debulking surgery combined with immune checkpoint inhibitors could be a curative treatment for advanced pediatric solid tumors.