Cytoreductive surgery (CRS) in combination with hyperthermic intraperitoneal chemotherapy (HIPEC) has been established as novel treatment approach for peritoneal sarcomatosis (PS). Despite of promising clinical reports, there is still a lack of knowledge regarding optimal drug combinations, treatment duration and local effects. To answer these questions, we intended to establish a murine animal model for further evaluation.
Human alveolar rhabdomyosarcoma cells were xenotransplanted into NOD/LtSz-scid IL2Rγnull-mice (n=96). In the control group, a continuously intraperitoneal lavage with isotonic saline solution (37° or 42°C, n=16) was used. In the treatment group, animals were treated with intraperitoneal cisplatin (30 or 60mg/m2) for 60 minutes at 37° or 42°C (n=16). Tumor dissemination was documented by the peritoneal cancer index (PCI) adapted for the animal model. Tumor samples were harvested at the end of the perfusion. Histopathological and immunohistochemical studies using H&E-, KI-67-, and Cleaved Caspase 3-staining were carried out. Apoptotic effects were evaluated by using TUNEL-assay method. Additionally, abdominal tumor spread was documented by 7-T-small animal MRI.
We found an extensive peritoneal dissemination in over 91% of the cases (Median PCI: 8). HIPEC was feasible without acute side effects. Immunohistochemistry using KI-67 revealed no early concentration- or temperature-dependent effects of cisplatin-based HIPEC on the tumors as there were no observed effects regarding the cell viability. Immunohistochemical investigation with Cleaved Caspase-3 and immunofluorescence microscopy using TUNEL-assay detected scattered apoptotic effects at the outer tumor surface. MRI scans confirmed the observed tumor dissemination.
This is the first successful animal model for evaluation of HIPEC in pediatric rhabdomyosarcoma in mice. Cisplatin-based HIPEC had no early effects on the proliferation whereas circumscribed apoptotic effects could be detected at the tumor surface. This model allows further insights on the possible efficiency of HIPEC in RMS. Further studies using other drug combinations and treatment will follow.