Paediatrics: Rhabdomyosarcoma

Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in childhood. It accounts for 6% of all childhood malignancies (commonly aged <10yrs). The majority of cases are sporadic. Most are either embryo-nal or alveolar (more aggressive) subtypes. Botryoid (good prognosis) and spindle cell types are also recognized. A small number of cases are associ-ated with Li–Fraumeni syndrome.

Presenting features 

Mass, pain and obstruction of:

·  bladder;

·  pelvis;

·  nasopharynx;

·  parameningeal;

·  paratestis;

·  extremity;

·  orbit;

·  intrathoracic.

Lymph node involvement is common. Distant metastases are rare.

Diagnosis and staging

·  Imaging of primary site: CT, or MRI.

·  Biopsy for histological molecular and cytogenetic analysis. Alveolar RMS characterized by the presence of t(2;13) or t(1;13).

·  CT scan of chest.

·  Bone marrow aspirates and trephines.

·  Isotope bone scan.

·  Lumbar puncture (parameningeal primaries).

Treatment

·  Chemotherapy (6–9 courses) with ifosfamide or cyclophosphamide, actinomycin, vincristine, anthracyclines.

·  Surgery is reserved for accessible sites (paratesticular, peripheral) after 3–6 courses of chemotherapy.

·  Radiotherapy after surgery for residual tumour and alveolar histology.

Prognosis 

Ranges from <10% survival for bony metastatic disease to >90% for excised paratesticular tumours. Favourable features are:

·  Younger age at diagnosis.

·  Botryoid or embryonal histology.

·  Paratesticular or superficial head and neck sites.

·  Absence of nodal involvement or distant metastases.

Off treatment monitoring 

Imaging of primary tumour site by US or MRI and CXRs to screen for pulmonary metastatic recurrence.

Relapse

·  Second-line chemotherapy.

·  Radiotherapy may be employed at sites not previously irradiated.

Outcome for relapse and recurrence is poor