Optimal Management Strategies for Rhabdomyosarcoma in Children

Rhabdomyosarcoma is the most common sarcoma of childhood. Fortunately, the goal of cure is realistic for the majority of patients with localized tumors. However, management of these patients remains challenging. The fact that the tumor arises in a wide variety of primary sites, some of which are associated with specific patterns of local invasion, regional lymph node spread, and therapeutic response, requires physicians to be familiar with site-specific staging and treatment details. In addition, rhabdomyosarcoma requires multimodality therapy that can be associated with significant acute toxicities and long-term effects, particularly when administered to young children. These factors sometimes present a dilemma as to the best approach to optimize the chance of cure, minimize toxicity, and respect quality of life. The purpose of this review is to discuss ‘optimal’ management of this complicated tumor. Since the tumor is relatively rare, requires highly specialized care, and important management questions remain to be answered, optimal management of rhabdomyosarcoma includes enrollment in clinical trials whenever possible. Appropriate management begins with establishing the correct pathologic diagnosis, histologic subtype, primary site, extent of disease (International Society of Pediatric Oncology [SIOP]-TNM-Union Internationale Contre le Cancer stage or Intergroup Rhabdomyosarcoma Study Group [IRSG] stage), and extent of resection (IRSG group). Cooperative groups throughout North America and Europe have defined risk-adapted treatment based on these factors; this treatment requires a coordinated management plan that includes surgery, chemotherapy, and usually radiotherapy. The surgical approach for rhabdomyosarcoma is to excise the primary tumor whenever possible without causing major functional or cosmetic deficits. Wide excision is difficult in some primary sites and can be complicated by the fact that the tumor grows in a locally infiltrative manner so that complete resection is often neither possible nor medically indicated. Incompletely resected tumors are generally treated with radiotherapy. The cooperative groups reduce the dose of radiation based on the response of the tumor to chemotherapy and delayed primary resection to differing degrees. Response-adjusted radiation administration may reduce the long-term effects of radiotherapy, such as bone growth arrest, muscle atrophy, bladder dysfunction, and induction of second malignant neoplasms; however, it may also be associated with an increased risk of tumor recurrence. All patients with rhabdomyosarcoma require chemotherapy. A backbone of vincristine and dactinomycin with either cyclophosphamide (VAC) or ifosfamide (IVA) has been established. Risk-adapted treatment involves reducing or eliminating the alklyating agent for patients with the most favorable disease characteristcs. Clinical trials are ongoing to improve outcomes for higher risk patients; newer agents, such as topotecan or irinotecan, in combination with VAC or use of agents in novel ways are being investigated. Acute and long-term toxicities associated with these chemotherapy regimens include myelosuppression, febrile neutropenia, hepatopathy, infertility, and second malignant neoplasms. A 5-year survival rate >70% has been achieved in recent trials for patients with localized rhabdomyosarcoma. However, the outcome for patients who present with metastatic disease remains poor. In the future, risk-adapted classification of rhabdomyosarcoma will likely be based on biologic features, such as the presence of chromosomal translocations or specific gene expression profiles. It is hoped that newer therapies directed at specific molecular genetic defects will benefit all patients with rhabdomyosarcoma.