Introduction
Peritoneal sarcomatosis (PS) in rhabdomyosarcoma (RMS) is a rare and the
most advanced tumor stage with wide intraperitoneal tumor spread in
children. Due to promising clinical reports, cytoreductive surgery (CRS)
in combination with hyperthermic intraperitoneal chemotherapy (HIPEC)
has been established as therapeutic option for PS . Nevertheless, this
treatment is still experimental in children and not successful in all
patients. The prognosis is sobering due to high probability of tumor
recurrence . In a retrospective study on CRS and HIPEC (including seven
cases of PS of RMS) the median over-all survival was 7.1 to 31.4 months
after succeeded tumor resection whereas the diseases-free survival was
described by 19.9 to 34 months depending on peritoneal cancer index
(PCI). After incomplete cytoreductive surgery, no patient survived
longer than 15 months . The evaluation of the intraperitoneal tumor
spread and the achievement of complete CRS plays an integral role and
might determine the therapeutic success . An enhancement of HIPEC by
additive modalities such as photodynamic therapy (PDT) might be
beneficial. The principle of PDT is a photosensitive agent, which
ideally accumulates selectively in tumor cells. After illumination with
light of the appropriate wavelength in the presence of oxygen the
photoactivated sensitizer generates highly reactive oxygen species (ROS)
leading to critical cytotoxicity and destruction of tumor cells via
apoptosis or necrosis . Furthermore, photosensitizer are known to show
fluorescence enabling visualization and focused resection of tumor
tissue during photodynamic diagnosis (PDD) . The natural photosensitizer
Hypericin (HYP), an extract from the St. John’s wort, represents an
ideal and promising agent for the challenging treatment of PS of RMS:
HYP with its strong self-fluorescence and low photobleaching has been
used successfully as photosensitizer for in vitro and in
vivo visualization and PDT of pediatric RMS . Up to now there are no
data on combining HYP and HIPEC in RMS in vivo . Therefore, we
tested a combination of the photosensitizer HYP with HIPEC in a recent
established murine HIPEC animal model of intraperitoneal disseminated
pediatric RMS.