Increasing the efficiency of hyperthermic intraperitoneal chemotherapy (HIPEC) by combination with a photosensitive drug in pediatric rhabdomyosarcoma in an animal model.

BACKGROUND: Cytoreductive surgery (CRS) in combination with hyperthermic intraperitoneal chemotherapy (HIPEC) is an option in advanced peritoneal sarcomatosis. Nevertheless, CRS and HIPEC are not successful in all patients. An enhancement of HIPEC using photodynamic therapy (PDT) might be beneficial. Therefore, a combination of the photosensitizer hypericin (HYP) with HIPEC was evaluated in an animal model. PROCEDURE: An established HIPEC animal model for rhabdomyosarcoma (NOD/LtSz-scid IL2Rγnullmice, n = 80) was used. All groups received HYP (100 µg/200 µl) intraperitoneally with and without cisplatin-based (30 or 60 mg/m2 ) HIPEC (37°C or 42°C, for 60 minutes) (five groups, each n = 16). Peritoneal cancer index (PCI) was documented visually and by HYP-based photodynamic diagnosis (PDD). HYP-based PDT of the tumor was performed. Tissue samples were evaluated regarding proliferation (Ki-67) and apoptosis (TUNEL). RESULTS: HYP uptake was detected even in smallest tumor nodes (<1 mm) with improved tumor detection during PDD (PCI with PDD vs. PCI without PDD: 8.5 vs. 7, p < .001***). Apoptotic effects after PDT without HIPEC were limited to the tumor surface, whereas PDT after HIPEC (60 mg/m2 , 42°C) showed additional reduction of tumor proliferation in the top nine to 11 cell layers (50 µm). CONCLUSION: HYP as fluorescent photosensitizer offers an intraoperative diagnostic advantage detecting intraperitoneal tumor dissemination. The combination of HYP and cisplatin-based HIPEC was feasible in vivo, showing enhanced effects on tumor proliferation and apoptosis induction across the tumor surface. Further studies combining HYP and HIPEC will follow to establish a clinical application.

Establishment of a new valid animal model for the evaluation of hyperthermic intraperitoneal chemotherapy (HIPEC) in pediatric rhabdomyosarcoma.

BACKGROUND: Cytoreductive surgery in combination with hyperthermic intraperitoneal chemotherapy has been established as a novel treatment approach for peritoneal sarcomatosis. Despite promising clinical reports, there is still a lack of knowledge regarding optimal drug usage and local effects. Therefore, we intended to establish a murine animal model for further evaluation. PROCEDURE: Alveolar rhabdomyosarcoma cells were xenotransplanted into NOD/LtSz-scid IL2Rγnullmice (n = 100). The mice received a continuous intraperitoneal lavage with isotonic saline solution as control or with cisplatin (30 or 60 mg/m2 ) as treatment group for 60 minutes at 37°C or 42°C (6 subgroups, each n = 16). Tumor spread was documented by an adapted peritoneal cancer index and MRI (n = 4). Tumor and tissue samples, harvested at the end of the perfusion, were evaluated regarding morphology, proliferation, and apoptosis (H&E-, Ki-67-, cleaved caspase 3-staining, TUNEL assay). RESULTS: Extensive peritoneal sarcomatosis in over 91% of the cases was observed. HIPEC was feasible without acute side effects. Ki-67 staining revealed concentration- or temperature-dependent effects of cisplatin-based HIPEC on the tumors. Although cleaved caspase-3 showed only sporadic apoptotic effects. TUNEL assay detected concentration- or temperature-dependent apoptotic effects at the outer tumor surface. MRI scans confirmed the observed tumor dissemination. CONCLUSION: This is the first animal model for evaluation of HIPEC in pediatric RMS in mice. Cisplatin-based HIPEC had 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.