What is Ewing’s sarcoma?
Ewing’s sarcoma accounts for 30% of all bone cancers, but it can sometimes also be found outside the bone. It was first described by James Ewing in 1921 as a form of bone cancer, that is, unlike a more common form of bone cancer (osteosarcoma), responsive to treatment with radiation.
Ewing’s sarcoma develops in a primitive (embryonic) cell after a mutation which is a spontaneous change in its genetic makeup happened. This mutation joins two different chromosomes to create a new gene that is constantly activated. The joining of two different chromosomes is a mutation that is called a translocation. One of the chromosomes involved in this translocation is chromosome 22 on which the Ewing sarcoma or EWS gene is located. In Ewing’s sarcoma, it is joined with another gene on a different chromosome, in most cases with the FL1 gene on chromosome 11. This new chimeric gene gives the cell the signal to grow uncontrolled thus transforming it into a cancer cell.
Ewing’s sarcoma most commonly appears in the middle of the big bones of the leg and arm (femur and humerus), but it is also common in the pelvis and in the chest near the ribs. The long-term survival of Ewing’s sarcoma depends on what stage the disease is in, when it is first diagnosed. For localized disease which means a single tumor that has not spread into other tissues, the long-term survival rate is around 80%, however, the survival rate is much lower, if the tumor has metastasized (spread) or does not respond to treatment.
What are the symptoms of Ewing’s sarcoma?
The symptoms of Ewing’s sarcoma are pain around the tumor, fatigue, fever, loss of appetite, weight loss, and swelling and/or redness around the tumor. If the tumor is in the spinal area, it can lead to paralysis and incontinence. If it compresses a nerve somewhere else this also can lead to numbness, tingling or paralysis in that area of the body.
How is Ewing’s sarcoma diagnosed?
Aside from a complete physical and medical history that evaluates the above mentioned symptoms, a number of specific diagnostic tests can be performed. X-rays will be able to show tumors in the bone and often the physician will be able to tell from the appearance on an x-ray, whether the tumor in the bone is benign or malignant. A bone scan which is a nuclear imaging method, can show whether the bone contains tissue that is more metabolically active or growths faster than the regular bone. This can either be due to a tumor or an injury to the bone. Together with an X-ray it can improve the ability of the physician to find the correct diagnosis. Other tests are magnetic resonance imaging (MRI) and computer tomography also known as CT or CAT scan. These show the body in much greater detail than regular X-rays and allow to see the connections of the tumor to the surrounding tissues and the blood circulation. These tests are also useful to see the extend of secondary tumors (metastases). Once a tumor is detected, a biopsy of the tumor tissue is done to determine whether the tumor is benign or malignant. A bone marrow aspiration or biopsy can also be ordered to see whether cancer cells have spread to the bone marrow. Since the Ewing’s sarcoma tumor cells look very similar to many other tumor cells, genetic tests can be done to detect the translocation that involve the EWS gene on chromosome 22 to make the final diagnosis.
What are the treatment options for Ewing’s sarcoma?
Surgery is a common treatment for Ewing’s sarcoma. The type of surgery that is going to be used depends on the extend of the tumor and its connections to the surrounding tissue. A common type of surgery is limb-sparing surgery in which the tumor and a part of the adjacent healthy tissue are cut out. However, if the physician determines that this type of surgery is not able to remove the entire tumor, maybe because the tumor involves nerve tissue and blood vessels, an amputation might be necessary. Nevertheless, the necessity of amputation is rare in Ewing’s sarcoma and there are other treatment options that can be used in addition or instead of surgery.
Ewing’s sarcoma is usually sensitive to radiation, so radiation therapy is often used in addition to limb-sparing surgery. In some cases, when the tumor has not yet reached a certain size, radiation therapy can also be used instead of surgery.
Chemotherapy is another treatment option for Ewing’s sarcoma. Often chemotherapy is prescribed 2-4 months prior to surgery to shrink the primary tumor and control the spreading of the disease within the bones or to other areas of the body, like for example to the lung. Chemotherapy consists of a regimen of cancer fighting drugs. As chemotherapy is a systemic treatment, which means it goes to every part of the body, it can also be used after surgery or radiation therapy to kill any cancer cells in the body that have not been removed by the surgery or radiation treatment. Chemotherapy can, depending on the specific drug or drugs used, either be given as pills, or as an injection or infusion directly into the blood stream. In particularly advanced cases or when the cancer does not respond to regular chemotherapy, a stronger chemotherapy regimen can be used. Since this has the side effect that it damages the blood cell-building stem cells in the bone marrow, it is called myoablative therapy and might require a stem cell transplant to replenish the stem cells in the bone marrow.