Ewing Sarcoma

Ewing Sarcoma

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What is Ewing Sarcoma?

Ewing Sarcoma is the second most common primary bone cancer in children and adolescents. It affects adolescents and young adults between 10 and 30 years of age. It occurs more commonly in males than females..

Ewing sarcoma is a primary tumor of small round cells that affects bones and soft tissues. A primary tumor is a tumor that arises from the particular organ and has not spread to that organ from another part of the body. Ewing sarcoma most commonly affects the bones of the lower limbs (41%), pelvis (26%), chest wall (16%), upper extremity (9%), spine (6%), hand and foot (3%) and skull (2%). It is more common in Caucasians than in Africans and Asians.

What is the Cause of Ewing Sarcoma?

The exact cause of Ewing sarcoma is unknown. A genetic change called a translocation is noted, most commonly between the chromosomes #11 and #22. A translocation is the shifting of genetic material between different chromosomes. The translocation in Ewing sarcoma is not inherited from parents but appears as a new mutation. Factors that lead to the development of the mutation are not known.

What are the Symptoms and Signs of Ewing Sarcoma?

Symptoms and signs of Ewing tumor include the following:
  • Localized pain. The pain is intermittent and mild initially but rapidly increases in intensity
  • Appearance of a lump in the arms, legs, chest or pelvis
  • The affected bone might fracture without any associated trauma or arthritis
  • Fever and weight loss may be present
Symptoms and Signs of Ewing Sarcoma

Stages of Ewing Sarcoma

Ewing sarcoma can be localized or metastatic.
  • Localized Ewing sarcoma - Localized Ewing sarcoma is limited to the bone or soft tissue in which it began. It may have spread locally to the same bone or to nearby lymph nodes.
  • Metastatic Ewing sarcoma - This cancer has spread from its point of origin to other parts of the body. Ewing sarcoma first spreads to the lungs and other bones, and then to the rest of the body.
Medical practitioners follow American Joint Committee on Cancer (AJCC staging) system of grading and Enneking’s system of grading to plan the treatment of Ewing sarcoma.

The AJCC staging system is used for cancers arising from the bone. It is based on (source: https://www.cancer.org/ ) -
  • T describes the size of the tumor and its spread to different areas of the same bone of origin
  • N describes the extent of spread to nearby lymph nodes
  • M describes whether the cancer has spread to other organs of the body
  • G describes the grade of the tumor cells, how much is normal or abnormal. Ewing sarcoma is considered high grade.

T categorizes sarcoma into -

  • T0: No evidence of a primary tumor
  • T1: The tumor is 8 cm or less across
  • T2: The tumor is bigger than 8 cm across
  • T3: The tumor is present in more than one site in the same bone

N categorizes sarcoma into -

  • N0: No spread of the carcinoma to nearby lymph nodes
  • N1: The carcinoma spreads to nearby lymph nodes

M categories of bone cancer -

  • M0: No spread to distant organs
  • M1a: The carcinoma has spread only to the lungs
  • M1b: The carcinoma has spread to other distant sites in the body

Grades of bone cancer -

  • GX: The grade of the cancer cannot be assessed
  • G1-G2: Low grade
  • G3-G4: High grade

Stage grouping

The final stage of the tumor is determined based on the T, N, and M categories and grade of the bone cancer.
  • Stage IA (T1, N0, M0, G1 to G2 (or GX)) - In this stage, size of the tumor is 8 cm across or less, is localized to the point of origin, is of low grade and has not spread to the nearby lymph nodes or to the distant parts of the body.
  • Stage IB (T2 or T3, N0, M0, G1 to G2 (or GX)) – In this stage, the tumor is either larger than 8 cm across in size or has spread to more than one place in the same bone. It is of low grade, or the grade cannot be assessed, and has not spread to nearby lymph nodes or to the distant parts of the body.
  • Stage IIA (T1, N0, M0, G3 to G4) – In this stage, the tumor is 8 cm across or less in size, and is localized to point of origin. It is of high grade but has not spread to nearby lymph nodes or to distant parts of the body.
  • Stage IIB (T2, N0, M0, G3 to G4) - In this stage, the tumor is larger than 8 cm across in size. It is of high grade and has not spread to nearby lymph nodes or to distant parts of the body.
  • Stage III (T3, N0, M0, G3 to G4) – In this stage, the tumor is of high grade and has spread to more than one place in the same bone, but has not spread to nearby lymph nodes or to distant parts of the body.
  • Stage IVA – In this stage, the tumor has spread only to the lungs but has not spread to the lymph nodes or to other distant sites.
  • Stage IVB – In this stage, the cancer has spread either to lymph nodes, or to distant sites other than the lungs.
Enneking Stages

Enneking system is based on the grade of tumor, site of tumor and level of cancer spread to other parts of the body. Under this system, tumors are graded as below:
  • Stage 1A – It is of low grade, but has not grown through the bone wall and neither has it spread to other parts of the body.
  • Stage 1B – It is of low grade, but has spread through the bone wall to nearby tissues.
  • Stage 2A – It is of high grade but localized to the bone of origin. It hasn’t yet spread to other nearby tissues, bones or other parts of the body.
  • Stage 2B - It is of high grade and has spread through the bone wall to nearby tissues.
  • Stage 3 – It is of high grade and has spread to other parts of the body like other bones and the lungs.

How is Ewing Sarcoma Diagnosed?

The medical practitioner will start the diagnosis with a complete medical history of the patient. The doctor examines the painful area of the patient and follows the examination by a series of diagnostic tests.
  • Blood tests – Abnormal complete blood count and elevated lactate dehydrogenase levels in the blood are associated with Ewing sarcoma and other cancers.
  • Imaging tests: Imaging tests help in detecting the extent of the disease spread and monitoring response to treatment. Various techniques used are conventional radiography (x-ray), magnetic resonance imaging (MRI), computerized tomography (CT scan), positron imaging (PET scan) and bone scintigraphy.
    • X ray of the painful area is taken. If the X-ray is found to be suspicious, advanced imaging techniques are done.
    • CT Scan of the painful area and chest are taken, since Ewing sarcoma first spreads to the lungs
    • MRI helps in determining the extent of spread of bone tumors, and the level up to which adjacent blood vessels and nerves have been impacted. MRI needs to be performed routinely for surgical planning. It helps in demonstrating lesions involving large segments of the intramedullary cavity and also, evaluating the extent of soft tissue masses affected by cancer spread.
    MRI Scan Helps to Diagnose Ewing Sarcoma
    • PET scan helps to determine the sites where the cancer has spread.
  • Biopsy
    • Excisional Biopsy – If the tumor is small, superficially placed with minimal compression to neighboring areas, the doctor removes the entire tumor, and sends it for pathological examination. This is called excisional biopsy.
    • Incisional Biopsy - If the tumor is large, deeply placed and compresses adjacent tissues, only a part of the tumor is removed. This is called incisional biopsy.
    • Bone Marrow Biopsy - A sample of bone marrow cells is removed and histopathological examination of the same is done for the presence of cancer cells. It helps to detect spread of the cancer to the bone marrow
  • Immunohistochemistry - The sample removed through biopsy is tested to identify substances that are found in Ewing sarcoma cells. This helps in confirming the diagnosis.
  • Cytogenetics - The cells in the sample removed through biopsy is examined for genetic changes of translocation that are characteristic for Ewing sarcoma.
  • Reverse transcription polymerase chain reaction - This test is done to detect the presence of translocation in the genetic material. It also helps in detecting residual or recurrent cancer.

What is the Prognosis or Outcome of Ewing Sarcoma?

The outcome of Ewing sarcoma depends on the following:
  • Site of origin. Ewing sarcoma, if originated in distal extremities (in hands or feet), has a better prognosis as compared to the proximal extremities (in the arms or thighs). If developed in the central sites, the prognosis is the worst
  • Extent of spread - Cancer that has spread to other parts of the body has poor outcomes
  • Extent of compression of adjacent tissues
  • Size of tumor
  • Age of the patient - Children younger than 15 years have a better prognosis
  • Gender of the patient - Girls have better prognosis than boys
  • First time tumor or recurrent - Recurrent cancer has a worse prognosis
The 5-year survival rate for Ewing sarcoma in the United States is around 78% for children less than 15 years of age, while it is 60% for adolescents between 15 and 19 years of age.

How is Ewing Sarcoma Treated?

  • Chemotherapy - Ewing sarcoma is a very aggressive cancer which requires a planned long cycle of treatment. The first step of choice for treatment is chemotherapy. 14 to 17 cycles of chemotherapy are required. It almost takes 6 to 9 months to treat cases with best prognosis. A multi-drug regimen is usually required for the treatment. In the United States and Europe, a five-drug regimen is administered with the drugs vincristine, doxorubicin, cyclophosphamide, ifosfamide, and etoposide. High-dose chemotherapy stem cell rescue is given in some case with poor prognosis. The patient’s stem cells are removed from the bone marrow before beginning of the treatment and are frozen. After the completion of chemotherapy, the stored stem cells are infused back to the patient. This is particularly helpful in the treatment of patients with recurrence of tumor.
Chemotherapy Helps Treat Ewing Sarcoma
  • Surgical Resection - Surgery is planned after the cancer has been reduced to a certain point by chemotherapy. Sometimes, complete or maximum possible removal of tumor might require amputation of the limb. In such cases, the surgery may be followed by artificial limb implantation or prosthetic reconstruction of the amputated limb.
  • Radiation therapy - Post surgery, radiation therapy cycles may be planned to kill the cancer cells that cannot be removed surgically. It is done by:
    • External radiation wherein the radiations are given from outside of the body using machines.
    • Internal radiation which uses needles or catheters inserted inside the patient’s body to deliver the radiation directly into the abnormal cells.

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