Rhabdomyosarcoma is a malignant tumor of mesenchymal origin with muscular differentiation. It accounts for about half of all soft tissue sarcomas in children aged 0 to 14, but represents a smaller proportion of all pediatric cancers. There is an initial peak in incidence among young children and another during adolescence.

The disease may remain localized, spread to nearby lymph nodes, or metastasize to distant sites. The primary sites of metastasis are the lungs, bones, and bone marrow. The frequency of lymph node involvement depends, in particular, on the tumor’s location and biological subtype.

Symptoms depend on the tumor's location. Any mass that grows in size—even if it is painless—should be examined.

Imaging

MRI is the preferred imaging modality for evaluating the primary tumor and its relationship to neighboring organs. A CT scan may be useful depending on the tumor’s location and is particularly helpful in detecting lung involvement. A PET-CT scan can aid in assessing disease extent and evaluating treatment response in certain protocols.

Biopsy

A biopsy is essential. It must be scheduled at a specialized center in collaboration with the team that will provide local treatment. The specimen must be sufficient for histopathological analysis, immunohistochemistry, and molecular testing, while avoiding a procedure that would complicate subsequent surgery.

Staging

The staging evaluation looks for lymph node involvement and lung, bone, or bone marrow metastases. Depending on the site and risk group, it may include whole-body imaging, bone marrow biopsies, a lumbar puncture for certain parameningeal locations, and the removal of a suspicious lymph node.

European guidelines identify several risk groups. The prognosis varies greatly between a small, localized tumor in a favorable location, locally advanced disease, and metastatic disease. The overall pediatric cure rate is close to 70 percent, but this average masks a wide range of very different situations.

Treatment is multimodal. Its duration and intensity are tailored to the risk group and the patient’s response. The goal is to achieve a cure while minimizing functional, cosmetic, urinary, sexual, endocrine, and growth-related sequelae.

Chemotherapy

Chemotherapy is traditionally based on vincristine, actinomycin D, and ifosfamide, with or without an anthracycline depending on the risk group. Treatment regimens evolve in line with international protocols and studies. For certain high- or very high-risk groups, maintenance chemotherapy with vinorelbine and low-dose cyclophosphamide is recommended following initial treatment.

Surgery

Surgery aims for microscopically complete resection with as few sequelae as possible. Primary surgery is reserved for small, easily accessible tumors. Deferred surgery may be offered after tumor reduction. Procedures resulting in functional or cosmetic impairment should not be performed without expert discussion of the alternatives.

External Beam Radiation Therapy

Radiation therapy contributes to local control when complete surgical resection is not possible, when a microscopic risk persists, or when the risk group warrants it. Doses, treatment volumes, and schedules are tailored to the tumor location, patient age, surgical status, and treatment response. Conformal techniques, intensity-modulated radiation therapy, or proton therapy may reduce exposure to certain healthy tissues.

Brachytherapy

Brachytherapy involves temporarily placing a radioactive source in contact with the tumor bed to deliver a high dose to a limited volume. It may be offered for selected sites, particularly genitourinary, gynecological, limb, or certain wall locations, when the anatomy and tumor volume allow for safe implantation. Its indication is not based on a single size threshold.

Local control is essential, but it must be achieved without unnecessarily imposing severe long-term consequences on a growing child. The combination of surgery, external beam radiation therapy, and brachytherapy depends on the tumor site, the response to treatment, the margins, the patient’s age, and the expected functional outcomes.

Metastatic forms require an intensive, individualized strategy that combines systemic treatment with monitoring of tumor sites whenever possible. In the event of a relapse, a new biopsy or characterization may be considered. Treatment depends on the time elapsed, the site, prior treatments, and the possibility of further local monitoring.

FaR-RMS is an international, multi-arm, multi-stage study focused on newly diagnosed and relapsed rhabdomyosarcomas. It evaluates several aspects of initial chemotherapy, the duration of maintenance therapy, the dose and schedule of radiation therapy, as well as new agents for very high-risk or relapsed disease.

The study also evaluates the use of PAX::FOXO1 status for risk stratification and the prognostic role of the response to PET-CT. Several questions may be open or closed at different times. Therefore, inclusion status must be verified in the institutional registry at the time of online submission.

Follow-up is intended to monitor for recurrence—most often in the first few years—and to detect late effects. It should continue beyond the end of growth, depending on the treatments received.

The Department of Pediatric and Adolescent Oncology coordinates patient care with the teams in imaging, pathology, molecular biology, partner surgical departments, radiation therapy, brachytherapy, supportive care, and long-term follow-up. Cases are discussed in specialized multidisciplinary team meetings.

Gustave Roussy is one of the coordinating centers of the NETSARC+ network. Depending on the location of the tumor, certain surgical procedures are organized with expert partners while maintaining a coordinated treatment strategy.