Before a biopsy of a suspected tumor mass is performed, imaging studies of the mass and baseline laboratory studies should be obtained. After the diagnosis of rhabdomyosarcoma has been made, an extensive evaluation to determine the extent of the disease should be done prior to instituting therapy. This evaluation should include a chest x-ray, computed tomography (CT) scan of the chest, bilateral bone marrow aspirates and biopsies, bone scan, magnetic resonance imaging of the base of the skull and brain (for parameningeal primary tumors only), and CT scan of the abdomen and pelvis (for lower extremity or genitourinary primary tumors).

A CT scan of regional lymph nodes should be considered. Enlarged lymph nodes should be biopsied. One study has demonstrated that sentinel lymph node biopsies can be safely performed in children with rhabdomyosarcoma, and tumor-positive biopsies may alter the treatment plan.[1] Positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (FDG) scans can identify areas of possible metastatic disease not seen by other imaging modalities.[2] However, the efficacy of these two procedures for identifying involved lymph nodes or other sites is under evaluation; these procedures are not required by current treatment protocols.

Terms used in this summary section are defined below in Table 1.

Table 1. Definition of Terms

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Term	Definition
Favorable site	Orbit; nonparameningeal head and neck; genitourinary tract excluding kidney, bladder, and prostate; biliary tract.
Unfavorable site	Any site other than favorable.
T1	Tumor confined to anatomic site of origin.
T2	Tumor extension and/or fixation to surrounding tissue.
a	Tumor ≤5 cm in maximum diameter.
b	Tumor >5 cm in maximum diameter.
N0	No clinical regional lymph node involvement.
N1	Clinical regional lymph node involvement.
NX	Regional lymph nodes not examined; no information.
M0	No metastatic disease.
M1	Metastatic disease.

Staging of rhabdomyosarcoma is relatively complex. The process includes the following steps:

1. Assigning a stage (consider site, size, Surgico-pathologic Group, and presence/absence of metastases).
2. Assigning a local tumor Surgico-pathologic Group (status postsurgical resection/biopsy, with pathologic assessment of the tumor margin).
3. Assigning a Risk Group (classified by Stage, Group, and histology).

As noted previously, prognosis for children with rhabdomyosarcoma depends on the primary site, size, Group, and histologic subtype. Favorable prognostic groups were identified in previous Intergroup Rhabdomyosarcoma Study Group (IRSG) studies, and treatment plans were designed on the basis of assignment of patients to different treatment groups according to prognosis. Several years ago, the IRSG merged with the National Wilms Tumor Study Group and with the two large cooperative pediatric cancer treatment groups to form the Children's Oncology Group (COG). New protocols for children with soft tissue sarcoma are developed by the Soft Tissue Sarcoma Committee of the COG (COG-STS).

Current COG-STS protocols for rhabdomyosarcoma use a TNM-based pretreatment staging system that incorporates the Surgico-pathologic Group, primary tumor site, regional lymph node status, and the presence or absence of metastases. This staging system is described in Table 2 below.[3,4]

Table 2. COG-STS Pretreatment Staging System

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Stage	Sites of Primary Tumor	T Stage	Tumor Size	Regional Lymph Nodes	Distant Metastasis
I	Favorable sites	T1 or T2	Any size	N0 or N1 or NX	M0
II	Unfavorable sites	T1 or T2	a, ≤ 5 cm	N0 or NX	M0
III	Unfavorable sites	T1 or T2	a, ≤ 5 cm	N1	M0
			b, > 5 cm	N0 or N1 or NX
IV	Any site	T1 or T2	Any size	N0 or N1 or NX	M1
M0 = absence of metastatic spread; M1 = presence of metastatic spread beyond the primary site; N0 = absence of nodal spread; N1 = presence of nodal spread beyond the primary site; X = unknown N status.

The IRSG Protocol I, IRSG Protocol II, and IRSG Protocol III studies prescribed treatment plans based on the Surgico-pathologic Group system. In this system, Groups are defined by the extent of disease and by the extent of initial surgical resection after pathologic review of the tumor specimen(s). The definitions for these Groups are shown in Table 3 below.[5,6]

Table 3. COG-STS Surgico-pathologic Group System

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Group	Definition
I (Approximately 13% of all patients are in this group.)	A localized tumor that is completely removed with pathologically clear margins and no regional lymph node involvement.
II (Approximately 20% of all patients are in this group.)	A localized tumor that is grossly removed with (a) microscopic disease at the margin, (b) involved, grossly removed regional lymph nodes, or (c) both (a) and (b).
III (Approximately 48% of all patients are in this group.)	A localized tumor with gross residual disease after incomplete removal or biopsy only.
IV (Approximately 18% of all patients are in this group.)	Distant metastases are present at diagnosis.

After patients are categorized by stage and Surgico-pathologic Group, a Risk Group is assigned. This takes into account stage, Group, and histology. Patients are classified for protocol purposes as having a low risk, intermediate risk, or high risk of disease recurrence.[7,8] Treatment assignment is based on Risk Group, as shown in Table 4.

Table 4. COG-STS Rhabdomyosarcoma Risk Group Classification

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Risk Group	Histology	Stage	Group
Low risk	Embryonal	1	I, II, III
	Embryonal	2, 3	I, II
Intermediate risk	Embryonal	2, 3	III
	Alveolar	1, 2, 3	I, II, III
High risk	Embryonal or Alveolar	4	IV

 [Note: Since 2006, patients with undifferentiated sarcomas are treated on the COG-STS protocol for non-rhabdomyosarcomatous soft tissue sarcoma. Refer to the PDQ summary on Childhood Soft Tissue Sarcoma for more information.]

References

1. Kayton ML, Delgado R, Busam K, et al.: Experience with 31 sentinel lymph node biopsies for sarcomas and carcinomas in pediatric patients. Cancer 112 (9): 2052-9, 2008.  [PUBMED Abstract]
   
   
2. Völker T, Denecke T, Steffen I, et al.: Positron emission tomography for staging of pediatric sarcoma patients: results of a prospective multicenter trial. J Clin Oncol 25 (34): 5435-41, 2007.  [PUBMED Abstract]
   
   
3. Lawrence W Jr, Gehan EA, Hays DM, et al.: Prognostic significance of staging factors of the UICC staging system in childhood rhabdomyosarcoma: a report from the Intergroup Rhabdomyosarcoma Study (IRS-II). J Clin Oncol 5 (1): 46-54, 1987.  [PUBMED Abstract]
   
   
4. Lawrence W Jr, Anderson JR, Gehan EA, et al.: Pretreatment TNM staging of childhood rhabdomyosarcoma: a report of the Intergroup Rhabdomyosarcoma Study Group. Children's Cancer Study Group. Pediatric Oncology Group. Cancer 80 (6): 1165-70, 1997.  [PUBMED Abstract]
   
   
5. Crist WM, Garnsey L, Beltangady MS, et al.: Prognosis in children with rhabdomyosarcoma: a report of the intergroup rhabdomyosarcoma studies I and II. Intergroup Rhabdomyosarcoma Committee. J Clin Oncol 8 (3): 443-52, 1990.  [PUBMED Abstract]
   
   
6. Crist W, Gehan EA, Ragab AH, et al.: The Third Intergroup Rhabdomyosarcoma Study. J Clin Oncol 13 (3): 610-30, 1995.  [PUBMED Abstract]
   
   
7. Raney RB, Anderson JR, Barr FG, et al.: Rhabdomyosarcoma and undifferentiated sarcoma in the first two decades of life: a selective review of intergroup rhabdomyosarcoma study group experience and rationale for Intergroup Rhabdomyosarcoma Study V. J Pediatr Hematol Oncol 23 (4): 215-20, 2001.  [PUBMED Abstract]
   
   
8. Breneman JC, Lyden E, Pappo AS, et al.: Prognostic factors and clinical outcomes in children and adolescents with metastatic rhabdomyosarcoma--a report from the Intergroup Rhabdomyosarcoma Study IV. J Clin Oncol 21 (1): 78-84, 2003.  [PUBMED Abstract]
   
   

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