Chapter 91

### Key Points

1. Overall 5-year survival for rhabdomyosarcoma has increased from 25% to 70% over the past 50 years.

2. Embryonal rhabdomyosacrcoma (ERMS) occurs in younger children and has a more favorable survival rate of 60%.

3. In patients with alveolar tumors (ARMS), the presence of regional nodes disease indicates a significantly worse prognosis, similar to metastatic disease, whereas in ERMS tumors the outcomes for patients with regional node disease is not any different than localized disease.

4. All patients with RMS receive some form of chemotherapy. Standard therapeutic regimens consist of a combination of vincristine, actinomycin-D, and cyclophosphamide (VAC).

5. Radiotherapy (RT) is an important adjunct to therapy for many children diagnosed with RMS, offering improved local control and outcomes.

6. A more aggressive surgical approach may be warranted for recurrent RMS and debulking is indicated in retroperitoneal tumors.

### Introduction

Prior to 1960, the pillar of therapy for rhabdomyosarcoma (RMS) was aggressive surgical resection, often including removal of a significant amount of normal tissue. Operations were often disfiguring and outcomes disappointing, with survival rates from 7% to 70% depending on tumor location. The addition of chemotherapy to the RMS treatment algorithm in 1961 improved these outcomes. The addition of radiotherapy (RT) in 1965 to select patients further improved outcomes and decreased the need for aggressive radical operations. Recognition of the crucial contribution of multimodal therapy to the treatment of RMS led to the establishment of the Intergroup Rhabdomyosarcoma Study Group (IRSG) in 1972. Subsequently, IRSG merged with other pediatric cooperative oncology groups in North American to form the Children's Oncology Group (COG). RMS studies were continued by the Soft Tissue Sarcoma Committee (STS) of the COG. With all of these efforts, the overall 5-year survival rate of RMS has increased from 25% to 70% (Fig. 91-1). However, these improvements in outcome have plateaued and now appear limited by the poor outcomes experienced in patients with metastatic or relapsed RMS.

###### Figure 91-1

Improvement in survival for RMS over the past 40 years.

### RMS Patient Demographics

In the first 2 decades of life, RMS is the most common form of soft-tissue sarcoma accounting for 4.5% of all cases of childhood cancer. It is the third most common extracranial solid tumor of childhood after Wilms tumor and neuroblastoma. Age at presentation follows a bimodal distribution with peak incidences between 2 and 6 years and again between 10 and 18 years of age. This distribution reflects the occurrence of the 2 major histologic subtypes of RMS: embryonal (ERMS) and alveolar (ARMS). The incidence of ERMS is highest at birth and extends through childhood but declines in adolescence. In contrast, the frequency of ARMS is low in infants and peaks during childhood and adolescence. Approximately 65% of all cases of RMS occur in children younger than 6 years of age. Slightly ...

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