Rhabdomyosarcoma (RMS) is an uncommon cancer originating in soft tissues like muscles, fat, and blood vessels. This aggressive cancer develops from primitive mesenchymal cells that normally differentiate into skeletal muscle. Metastatic RMS means the cancer has spread from its initial site to other parts of the body.
Understanding Metastatic Rhabdomyosarcoma
Rhabdomyosarcoma develops from cells meant to become skeletal muscle. While it can appear almost anywhere, common primary locations include the head and neck, genitourinary system (urinary and genital organs), and extremities (arms and legs). Approximately 15% to 20% of children with RMS are diagnosed with metastatic disease at initial presentation.
The most common subtypes are embryonal rhabdomyosarcoma (ERMS) and alveolar rhabdomyosarcoma (ARMS). ERMS accounts for 60-70% of childhood cases, affecting younger children, often in the head and neck or genitourinary tract. ARMS is the second most common, comprising 20-30% of cases, and is often more aggressive. It often affects older children, teenagers, and young adults, frequently developing in the arms, legs, or trunk. The pleomorphic subtype is less common in children, typically affecting adults over 50 and is also considered aggressive.
Rhabdomyosarcoma spreads through the bloodstream (hematogenous spread) and the lymphatic system. Cancer cells detach from the primary tumor, enter these systems, and travel to distant sites, forming new tumors.
The most frequent sites for metastatic rhabdomyosarcoma include the lungs (about 47% of cases), bone marrow (approximately 38%), bones (about 34%), and distant lymph nodes (about 26%).
Recognizing the Signs
Symptoms of metastatic rhabdomyosarcoma vary depending on the original tumor’s location and where the cancer has spread. A growing, painless lump or swelling is a common initial symptom, especially in the neck, chest, back, or extremities. As the tumor grows, it can press on surrounding tissues, causing discomfort or pain.
If cancer spreads to the lungs, symptoms may include a persistent cough or shortness of breath. Bone pain can indicate metastasis to the bones. Bone marrow involvement may manifest as easy bruising, bleeding, fatigue, or recurrent infections due to impaired blood cell production. Tumors in the head or neck can cause headaches, nasal congestion, or changes in vision.
Spread to the urinary or reproductive system can lead to blood in the urine, difficulty urinating, or changes in bowel movements. General signs of advanced cancer may also be present, including unexplained weight loss, fever, or persistent fatigue. It is important to seek medical attention for any persistent or unusual symptoms.
Confirming the Diagnosis
Diagnosis typically begins with a physical examination, followed by specialized tests. A biopsy, which involves removing a tissue sample for laboratory analysis, is the definitive method for confirming cancer. The tissue is examined under a microscope to identify cancer cells and determine the specific subtype.
Various imaging tests pinpoint the primary tumor’s location and detect spread. Magnetic Resonance Imaging (MRI) is often preferred for evaluating the primary tumor, offering detailed views of soft tissues, muscles, and bones, particularly in areas like the head, neck, arms, legs, and pelvis. Computed Tomography (CT) scans provide cross-sectional images, useful for evaluating tumors in the chest, abdomen, pelvis, or lymph nodes, and for detecting lung metastases.
Positron Emission Tomography (PET) scans, often combined with CT (PET/CT), identify metabolically active cancer cells throughout the body, helping detect lymph node involvement and distant metastases. Bone scans check for cancer spread to the bones. If bone marrow involvement is suspected, a bone marrow aspiration and biopsy may be performed, typically from the hip bone, to examine for abnormal cells.
Treatment Approaches
Treating metastatic rhabdomyosarcoma involves a multidisciplinary approach, combining several modalities to target cancer cells. The specific treatment plan is individualized, considering the cancer’s location, size, subtype, extent of spread, patient’s age, and overall health. This integrated approach aims to control the disease, reduce tumor burden, and improve outcomes.
Chemotherapy often serves as the initial systemic treatment. It uses anti-cancer drugs, such as vincristine, actinomycin D, and cyclophosphamide or ifosfamide, that circulate throughout the bloodstream to kill cancer cells. Chemotherapy aims to shrink tumors and destroy microscopic disease, often administered before other treatments.
Radiation therapy uses high-energy rays to damage and destroy cancer cells. This localized treatment often targets the primary tumor site or specific metastatic lesions, such as those in the brain, spinal cord, or lungs, to achieve local control.
Surgery plays a role in treatment, primarily for diagnosis through biopsy, and for removing the primary tumor or resectable metastatic lesions when feasible. Surgery of the primary site is often performed, even if complete removal of all cancer cells is not possible in widespread metastatic disease.
Newer approaches, such as targeted therapy and immunotherapy, are also being explored. Targeted therapies focus on specific molecular characteristics of cancer cells, aiming to inhibit their growth or survival. Immunotherapy works by boosting the body’s immune system to recognize and destroy cancer cells.
Navigating the Outlook
The prognosis for metastatic rhabdomyosarcoma is serious, though advancements in multidisciplinary treatment have improved outcomes. The overall cure rate for metastatic disease remains below 30%, especially with widespread spread at diagnosis. Ongoing research seeks more effective therapies.
Several factors influence the outlook. These include the patient’s age, the specific rhabdomyosarcoma subtype (alveolar histology is associated with a poorer outlook), and the primary tumor’s location. The extent of metastasis, particularly bone or bone marrow involvement and the number of metastatic sites, also significantly impacts prognosis. Response to initial treatment is another important indicator.
Long-term follow-up care monitors for cancer recurrence and addresses potential late effects from treatment. These can include issues with bone growth, fertility, and a risk of developing a second cancer. Regular check-ups are scheduled frequently in the initial years after treatment, with intervals lengthening over time.
Support systems are invaluable for patients and their families. Resources can provide emotional, practical, and financial assistance. These help individuals and families cope with treatment demands, manage side effects, and improve quality of life.