Cancer Health Center

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Most cases of rhabdomyosarcoma occur sporadically, with no recognized predisposing factor or risk factor.[12] For patients with embryonal tumors, high birth weight and large size for gestational age are associated with an increased incidence of rhabdomyosarcoma.[13] Genetic conditions associated with rhabdomyosarcoma include Li-Fraumeni cancer susceptibility syndrome (with germline p53 mutations),[14,15,16] neurofibromatosis type I,[17] Costello syndrome (with germline HRAS mutations),[18,19,20] Beckwith-Wiedemann syndrome (with which Wilms tumor and hepatoblastoma are more commonly associated),[21,22] Noonan syndrome,[23] and MEN2A.[24]

The prognosis for a child or adolescent with rhabdomyosarcoma is related to the age of the patient, site of origin, widest diameter of the tumor, resectability, presence of metastases, number of metastatic sites or tissues involved, presence or absence of regional lymph node involvement, histopathologic subtype (alveolar vs. embryonal), and delivery of radiation therapy (RT) in selected cases,[7,8,25,26,27,28,29,30,31]; [32][Level of evidence: 3iiiA] as well as unique biological characteristics of rhabdomyosarcoma tumor cells.[33] It is unclear whether response to induction chemotherapy, as judged by anatomic imaging, correlates with the likelihood of survival in patients with rhabdomyosarcoma, as one study found an association and another study did not.[34][Level of evidence: 3iiA]; [35] Examples of both clinical and biological factors with proven or possible prognostic significance are briefly described below.

• Children aged 1 to 9 years have the best prognosis, while those younger and older fare less well. In recent Intergroup Rhabdomyosarcoma Study Group (IRSG) trials, 5-year failure-free survival (FFS) was 57% for patients younger than 1 year, 81% for patients aged 1 to 9 years, and 68% for patients older than 10 years. Five-year survival for these groups was 76%, 87%, and 76%, respectively.[6] Infants may do poorly because their bone marrows are less tolerant of chemotherapy doses which older children can receive, thus infants are relatively underdosed compared to older patients. In addition, infants younger than 1 year may be less likely to receive radiation therapy for local control, because of concern for the high incidence of complications in this age group. In older children, vincristine and dactinomycin have upper dosage limits based on body surface area and these patients may also require reduced vincristine doses because of neurotoxicity.[9,26,36] Historical data show that adults fare worse than children (5-year overall survival rates, 27% � 1.4% and 61% � 1.4%, respectively; P < .0001).[37]
• Primary sites with more favorable prognoses include the orbit and nonparameningeal head and neck, paratestis, vulva, vagina, uterus (nonbladder, nonprostate genitourinary tract), and biliary tract.[7,8,38,39,40]
• Tumor burden at diagnosis has prognostic significance. Patients with smaller tumors (<5 cm) have improved survival compared with children with larger tumors.[7,38] Both tumor volume and maximum tumor diameter are associated with outcome.[34][Level of evidence: 3iiA] A retrospective review of soft tissue sarcomas in children and adolescents suggests that the 5 cm cutoff used for adults with soft tissue sarcoma may not be ideal for smaller children, especially infants. The review identified an interaction between tumor diameter and body surface area (BSA).[41] This was not confirmed by a Children's Oncology Group study of patients with intermediate-risk rhabdomyosarcoma.[42] This relationship requires prospective study to determine the therapeutic implications of the observation.
• Anaplasia is observed in 13% of cases of rhabdomyosarcoma and its presence may adversely influence clinical outcome in patients with intermediate-risk embryonal rhabdomyosarcoma.[43]
• Children with metastatic disease at diagnosis have the poorest prognosis. The prognostic significance of metastatic disease is modified by tumor histology (embryonal is more favorable than alveolar), the site of metastatic disease, and the number of metastatic sites.[27,44,45] Similarly, patients with metastatic genitourinary (nonbladder, nonprostate) primary tumors have a more favorable outcome than do patients with metastatic disease from primary tumors at other sites.[46] In addition, patients with otherwise localized disease but with proven regional lymph node involvement have a poorer prognosis than do patients without regional nodal involvement.[30,31]
• The extent of disease following the primary surgical procedure (i.e., the Surgico-pathologic Group, formerly called the Clinical Group) is also correlated with outcome.[7] In the IRS-III study, patients with localized, gross residual disease after initial surgery (Surgico-pathologic Group III) had a 5-year survival rate of approximately 70% compared with a more than 90% 5-year survival rate for patients with no residual tumor after surgery (Group I) and an approximate 80% 5-year survival rate for patients with microscopic residual tumor following surgery (Group II).[7,25]
• The alveolar subtype is more prevalent among patients with less favorable clinical features (e.g., younger than 1 year or older than 10 years, extremity primary tumors, and metastatic disease), and is generally associated with a worse outcome. In the IRS-I and IRS-II (POG-7898) studies, the alveolar subtype was associated with a less favorable outcome even in patients whose primary tumor was completely resected (Group I).[39] Statistically significant differences in survival for histopathologic subtype were not noted when all patients with rhabdomyosarcoma were analyzed,[47,48] and differences were not noted by histologic subtype in a large group of German children with rhabdomyosarcoma.[38] In the IRS-III study, outcome for patients with Group I alveolar subtype tumors was similar to that for other patients with Group I tumors, but the patients with alveolar subtype tumors received more intensive therapy.[7,49]

  Patients with alveolar rhabdomyosarcoma who have regional lymph node involvement have significantly worse outcomes (5-year failure-free survival [FFS] 43%) than patients who do not have regional lymph node involvement (5-year FFS 73%).[49]

• Adult patients with rhabdomyosarcoma have a high incidence of pleomorphic histology (19%). Pleomorphic histology is extremely rare in children and young adults with rhabdomyosarcoma. Adults have a higher incidence of tumors in unfavorable sites compared with children.[37]