Rhabdomyosarcoma

Definition:

• Malignant tumor of skeletal muscle lineage.
• Most common soft tissue sarcoma in children.

Epidemiology

• Peak incidence: 0–10 years
• Slight male predominance
• Common sites: head/neck, genitourinary tract, extremities

Clinical Features

• Painless, enlarging soft tissue mass
• Symptoms depend on location:
  • Head/neck → nasal obstruction, proptosis
  • Genitourinary → hematuria, urinary obstruction
  • Extremity → limb swelling, mass
• Advanced disease → metastases to lungs, bone marrow, bone

Subtypes

• Embryonal – most common, better prognosis
• Alveolar – less common, more aggressive, often associated with PAX3/7-FOXO1 fusion

Treatment & Pharmacist Role

1. Surgery

• Maximal safe resection when feasible

2. Chemotherapy (backbone: VAC regimen)

• Vincristine: neuropathy risk, dose-limited (2 mg max)
• Actinomycin D (Dactinomycin): myelosuppression, mucositis
• Cyclophosphamide: hemorrhagic cystitis → always give MESNA + hydration

3. Radiotherapy

• Often used for residual disease or unresectable tumors

4. Pharmacist Considerations

• Monitor hematologic toxicity (neutropenia, thrombocytopenia, anemia)
• Supportive care: hydration, antiemetics, growth factor support as needed
• Monitor neuropathy (vincristine) and renal/bladder toxicity (cyclophosphamide)
• Dose adjustments for age, renal/hepatic impairment

High-Yield Pharmacist Pearls

• VAC = Vincristine + Actinomycin D + Cyclophosphamide → memorize for BPS
• Cyclophosphamide → hemorrhagic cystitis prevention with MESNA
• Embryonal RMS → better prognosis; alveolar RMS → worse prognosis
• Long-term follow-up: watch for secondary malignancies, growth issues, fertility