BEVACIZUMAB EFFECT ON TOPOTECAN PHARMACOKINETICS ...

1.3 Rh30 Rhabdomyosarcoma as a Tumor Model
1.3.1 Rhabdomyosarcoma
Rhabdomyosarcoma (RMS) arises from immature cells that are developed to form
striated skeletal muscle, but it can virtually arise at any site and in any tissue in the body
except bone [102]. Head and neck are the most common regions where RMS occurs
(approximately 40%); the genitourinary sites and the extremities are the next most
frequent regions where RMS arises (approximately 20% each); and the remaining 20%
RMS initiates from other sites, such as parameningeal sites and the retroperitoneum
[103].
The two most common pathologic types of RMS are embryonal and
alveolar[102]. Embryonal rhabdomyosarcoma (ERMS) is the most common RMS seen in
infants and young children, comprising of more than 60% of all RMS. The ERMS cells
[104] exhibit the normal developing muscle cells, such as stellate undifferentiated
mesenchymal cells, elongated myoblasts, multinucleated myotubes, and fully
differentiated myofibers. ERMS has a better prognostic outcome [105-107] than other
subtypes and tends to occur in the genitourinary tract, head and neck, and abdomen.
About 20% of all rhabdomyosarcoma are of the alveolar histology (ARMS) [108], in
which cells look like the mature muscle cells in a 10-week-old fetus. ARMS grows much
faster than ERMS, needs more intensive treatment, has a higher relapse incidence and
worse prognostic outcome[109].
RMS occurs more frequently in children and adolescents (