Answer
Multiple clinical and biologic factors have been shown to influence the prognosis for a child with rhabdomyosarcoma. These include site of tumor origin, tumor size, nodal involvement, histology, and cellular DNA content. Staging classifications based on these factors allow the clinician to determine an overall prognosis for each patient. [12]
The site of origin influences the patient's clinical outcome. For example, patients with head and neck rhabdomyosarcoma affecting the orbit and nonparameningeal area have a prognosis more favorable than that of patients with tumors in other sites in the body. A study by Affinita et al of pediatric patients with nonparameningeal head and neck rhabdomyosarcoma reported that the lesions tended to display favorable characteristics, with 72.7% being under 5 cm, 72.7% being classified as T1, and 80.3% being classified as N0. The 10-year overall and progression-free survival rates for the patients—who underwent primary surgery or received chemotherapy along with delayed surgery and/or radiotherapy—were 74.2% and 65.1%, respectively. [13]
Another prognostic factor is tumor burden. Individuals with tumors smaller than 5 cm have an improved prognosis when compared with those with larger tumors. Children with regional nodal involvement do worse than those without nodal disease. Children with metastatic disease have the poorest prognosis. In this group, the most important prognostic factors are histologic subtype and the patient's age at diagnosis. For patients who are younger than 10 years and who have metastatic disease of embryonal histology, the 5-year survival rate is 60%. Patients older than 10 years with embryonal histology and all patients with alveolar histology have 5-year survival rates of less than 30%. [14]
Nutritional status also appears to be prognostically significant in children with rhabdomyosarcoma; a literature review by Joffe et al found that in the presence of this disease, pediatric patients with an abnormal body mass index (BMI) trend toward worse overall survival. [15]
The final clinical factor affecting the patient's prognosis is the extent of disease following initial surgical resection. As discussed in Staging Information below, the clinical groups established in the IRS-III and IRS-IV are partially based on the extent of disease after initial surgical resection. Patients without residual disease (group I) have a 90% 5-year survival rate. In patients with microscopic residual disease (group II), survival decreases to 80%, and those with gross disease after surgery (group III) have a 5-year survival rate of 70%.
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Embryonal rhabdomyosarcoma is evidenced by a variable cell population consisting of small, round tumor cells with hyperchromatic nuclei and of large, polygonal-shaped tumor cells with abundant eosinophilic cytoplasm, which often contains diagnostic cross striations (arrow). Image provided by Scott Kilpatrick, MD, Department of Pathology, University of North Carolina Hospitals.
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Alveolar rhabdomyosarcoma is evidenced by uniform cell population consisting of cells with a high nuclear-to-cytoplasmic ratio. The cells are arranged in variably sized nests separated by fibrous tissue septa. In places, the cells appear loosely dispersed, mimicking a pulmonary alveolar pattern. Image provided by Scott Kilpatrick, MD, Department of Pathology, University of North Carolina Hospitals.
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Axial CT scan of rhabdomyosarcoma in the left middle ear. Image provided by Suresh Muhkerji, MD, Department of Radiology, University of North Carolina Hospitals.
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Axial CT scan of left orbital rhabdomyosarcoma. Image provided by Suresh Muhkerji, MD, Department of Radiology, University of North Carolina Hospitals.
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Axial CT scan of right masticator space rhabdomyosarcoma. Image provided by Suresh Muhkerji, MD, Department of Radiology, University of North Carolina Hospitals.
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MRI of right masticator space rhabdomyosarcoma. Image provided by Suresh Muhkerji, MD, Department of Radiology, University of North Carolina Hospitals.
