Rhabdomyosarcoma

Rhabdomyosarcoma is rapidly growing and usually very malignant tumor, and rhabdomyosarcoma tumors are responsible for over 50% of soft tissue sarcomas seen in children. Rhabdomyosarcoma tumors arise from a cell called a "rhabdomyoblast", which is a primitive muscle cell, and instead of routinely differentiating into normal striated muscle cells, the malignant rhabdomyoblasts begin to grow out of control forming a rhabdomyosarcoma. Since striated muscle is located throughout the entire body, the rhabdomyosarcoma tumors can occur at numerous locations. The four most common sites in which rhabdomyosarcoma can be found are:

• head and neck; includes near the eye; inside nasal sinuses/throat; near the spine in the neck (35-40% )
• urinary & reproductive organs (genitourinary tract); bladder, prostate, any female organs (20% )
• extremities, i.e., arms &legs (15-20% )
• chest , lungs, abdomen (trunk area) (10-15% )

Rhabdomyosarcoma tumors located at external sites will often cause a visible & noticeable lump on a child's body.  The symptoms of internal rhabdomyosarcoma depend upon its location.  For example, rhabdomyosarcoma tumors in the nasal passage may lead to difficulty breathing; a bladder tumor can cause trouble urinating; an orbital tumor may cause the eye to protrude.

There are two (2) primary types of rhabdomyosarcoma and they are determined by the histology of the cells or how they look under a microscope:

Embryonal rhabdomyosarcoma (ERMS) is the most common type of rhabdomyosarcoma and is usually found in infants and younger children in the head and neck area, bladder, vagina, prostate and testes.

Alveolar type is a more aggressive tumor which usually occurs in the large muscles of the trunk, arms and legs.  Alveolar rhabdomyosarcoma (ARMS) typically affects older children or teenagers. 

Embryonal rhabdomyosarcoma is considered the most treatable form of the disease. The prognosis is affected by the location and stage of the primary tumor, age of the patient, respectability of tumor, presence of metastases and number of organs with tumor and lymph node involvement. Orbital and genitourinary track rhabdomyosarcomas have a better prognosis than do tumors which originate in the head and neck, extremity, pelvic, and trunk locations.  An excellent overview of rhabdomyosarcoma tumors can be found on the American Cancer Society's website:  What is Rhabdomyosarcoma?

TREATMENT

Children's Oncology Group is currently enrolling patients (age 3-21 years) in a Phase I study for NTX-010 in the treatment of pediatric rhabdomyosarcoma tumors. Treatment is administered as a single 100mL intravenous infusion over 1 hour. NTX-010 is a naturally occurring virus that has shown to be very effective in treating rhabdomyosarcoma tumors in pre-clinical studies. Patients previously treated with NTX-010 have only had minimal flu-like symptoms lasting 2-3 days and no typical chemotherapy side effects.