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Rhabdomyosarcoma: Staging, Grading, Risk Stratification, Treatment

Sarcoma Committee of the Children’s Oncology Group prescribed system is mostly used for assigning a stage, clinical group, and risk group to RMS.

Staging: TNM system is used for assigning a stage to RMS. “T” stands for “Tumor Size” and invasiveness, “N” for “Lymph Nodes”, and “M” for “Metastasis”. Numbers and/or letters after T (1, 1a, 1b, 2, 2a, and 2b), N (0 and 1), and M (0 and 1) provide more details about each of these factors.

Additionally, the sites of RMS are grouped into favorable (F) and unfavorable (UF) based on the prognosis of disease at different sites. Favorable sites include Orbit (eyeball); head and neck area except the para-meningeal area (nasal passages and nearby sinuses, middle ear, and the uppermost part of the pharynx); genitourinary tract except the kidney, bladder, and prostate; and the biliary duct. All other sites are considered as unfavorable.

Once T, N, and M categories and the site of a tumor are determined through different diagnostic techniques, this information is combined to assign an overall stage (from 0 to IV) to the disease. Following table describes the characteristics of different stages assigned to RMS:

STAGE STAGE and TNM DESCRIPTION
I F; Any T, Any N, M0 The primary tumor is present at a favorable site, which may be of any size. It may or may not have invaded into a nearby tissue and/or spread to nearby lymph nodes, but has not spread to distant body parts.
II UF; T1a-2a N0 M0 The primary tumor is present at an unfavorable site, which is </=5 cm in size. It may or may not have invaded into a nearby tissue, but has not spread to nearby lymph nodes. No spread to distant body parts.
III UF; T1a-2a N1 M0 The primary tumor is present at an unfavorable site, which is </=5 cm in size. It may or may not have invaded into a nearby tissue, but has spread to nearby lymph nodes. No spread to distant body parts.
UF; T1b-2b N0 M0 The primary tumor is present at an unfavorable site, which is >5 cm in size. It may or may not have invaded into a nearby tissue and/or spread to nearby lymph nodes. No spread to distant body parts.
IV Any site; Any T Any N M1 The primary tumor is present at a favorable or an unfavorable site. It may be of any size. It may or may not have invaded into a nearby tissue and/or spread to nearby lymph nodes. It has spread to distant body parts, like the lungs, liver, bones, or bone marrow.

Clinical Grouping: Based on the extent of the disease and the extent of primary surgical/biopsy excision, RMS is assigned a clinical group as described in the following table:

CLINICAL GROUP DESCRIPTION
I A localized tumor that has been completely removed by surgery/biopsy with negative/clear margins and no sign of lymph node involvement (no cancer left behind).
II A localized tumor that has been completely removed by surgery/biopsy with a microscopic positive margin and/or sign of lymph node involvement (minor cancer left behind).
III A localized tumor that was not completely removed by surgery/biopsy with a positive margin. Sign of lymph node involvement may be present but no sign of disease spread to distant body parts.
IV The diagnosis has revealed the spread of disease to distant body parts or presence of cancer cells in the cerebral spinal fluid, pleural, or peritoneal fluids.

Risk Stratification: Based on the overall stage, clinical group, and type of RMS (embryonal or alveolar), a risk group is assigned to the disease. Risk group helps in selecting appropriate treatment for the disease.

Following table describes the characteristics of the disease according to different risk groups:

RISK GROUP DESCRIPTION
Low risk Embryonal RMS; TNM stage 1; and Clinical groups I, II, or III

OR

Embryonal RMS; TNM stage 2 or 3; and Clinical groups I or II
Intermediate risk Embryonal RMS; TNM stage 2 or 3; and Clinical group III

OR

Alveolar RMS; TNM stage 1, 2, or 3; and Clinical groups I, II, or III
High-risk Embryonal/Alveolar RMS; TNM stage 4; and Clinical group IV

TREATMENT

Pleomorphic RMSs are usually treated with a treatment approach similar to that for other STSs. For the treatment of embryonal and alveolar RMS, patients should refer to institutions with experience in treating RMS.

All children and adults with RMS are treated with a multimodality treatment approach. Chemotherapy, surgery and/or radiotherapy is usually the part of the multimodality treatment approach. The surgery may be performed before chemotherapy, if possible, without any significant functional disability or other major cosmetic issues.

Otherwise, chemotherapy and/or radiotherapy are employed as first-line treatment. In case of the sufficient shrinkage in the tumor to render it resectable, surgery may be employed to remove all cancerous tissue. All these treatments may be employed separately or in combination when the tumor continues to grow or comes back after the initial treatment.

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