Ewing sarcoma is a rare cancer that forms in bone or the soft tissue surrounding bones. It is most frequently diagnosed in children, teenagers, and young adults, with the peak incidence occurring between the ages of 10 and 20, accounting for about 2% of all childhood cancers. While the exact cause remains unknown, it is characterized by a specific genetic change involving a translocation between chromosomes. This genetic anomaly results in the formation of a fusion gene, which is a hallmark of the disease and is identified in the tumor cells.
Symptoms and Common Locations
The initial signs of Ewing sarcoma can be subtle and are often mistaken for common injuries or growing pains. The most frequent symptom is localized pain at the tumor site, which may be intermittent at first but tends to become constant and often worsens at night. This pain may be accompanied by swelling, tenderness, or a noticeable lump, particularly if the tumor is in a bone close to the skin’s surface in the arms or legs.
Some individuals may also experience systemic symptoms, including a persistent low-grade fever, a general feeling of fatigue, and unexplained weight loss. In some cases, the first indication of Ewing sarcoma is a bone fracture from a minor injury. This type of break, known as a pathologic fracture, occurs because the tumor has weakened the bone.
Ewing sarcoma can develop in any bone or soft tissue, but it is most common in certain locations. The pelvis is one of the most frequent sites, along with the long bones of the legs (femur and tibia) and the upper arm (humerus). The ribs and the bones of the spine are also common locations. A tumor in the spinal region can press on nerves, leading to symptoms like numbness, tingling, or paralysis.
Diagnosis and Staging
The diagnostic process begins with a physical examination and a review of the patient’s medical history. If a bone tumor is suspected, imaging studies are ordered to visualize the affected area. X-rays are the first imaging test performed, and a doctor may then order a computed tomography (CT) or magnetic resonance imaging (MRI) scan for more detailed images. A CT scan helps determine the tumor’s size and shape, while an MRI is useful for visualizing its extent in surrounding soft tissues.
Further imaging, such as a positron emission tomography (PET) scan or a bone scan, is used to determine if the cancer has spread. A PET scan can detect cancer cells throughout the body by using a radioactive sugar that is absorbed by rapidly growing cells. A bone scan involves injecting a small amount of radioactive material that collects in areas of abnormal bone growth, highlighting potential cancer.
A definitive diagnosis requires a biopsy, which involves taking a small sample of the tumor tissue for examination by a pathologist. A biopsy can be performed in two ways: a needle biopsy, where a thin needle is inserted into the tumor to withdraw a sample, or a surgical biopsy, where an incision is made to remove a piece of the tumor. The biopsy confirms the presence of Ewing sarcoma cells. Once confirmed, the cancer is staged as either localized (confined to the primary site) or metastatic (spread to other parts of the body).
Treatment Approaches
Treatment for Ewing sarcoma is a multi-modal approach that combines several therapies. Chemotherapy is almost always used as a systemic therapy, where drugs travel through the bloodstream to reach and destroy cancer cells throughout the body. It is administered in two phases: neoadjuvant chemotherapy is given before surgery or radiation to shrink the tumor, and adjuvant chemotherapy is given after to eliminate remaining cancer cells and reduce the risk of recurrence.
Surgery aims for the complete removal of the tumor, and the type performed depends on its location and size. In many cases, limb-sparing surgery is possible, where the tumor and a margin of healthy tissue are removed, and the bone is reconstructed with a graft or prosthesis. In some situations, amputation may be necessary to ensure all of the cancer is removed, particularly if the tumor is very large or involves major nerves and blood vessels.
Radiation therapy is also used in treatment. It may be the primary local treatment if a tumor cannot be surgically removed without causing significant damage. Radiation can also be used after surgery to kill any remaining microscopic cancer cells or to treat areas where the cancer has spread. Newer forms like proton beam therapy deliver a more targeted dose of radiation, minimizing damage to healthy tissues.
Prognosis and Survival Rates
The prognosis for Ewing sarcoma is influenced by several factors. The most significant is whether the cancer is localized or has metastasized at the time of diagnosis. The tumor’s location and size, the patient’s age, and how well the cancer responds to initial chemotherapy also affect the outlook. The prognosis for patients with localized Ewing sarcoma has improved significantly with modern multi-modal treatment approaches.
Survival rates are reported as 5-year survival rates, which represent the percentage of patients who are still alive five years after their diagnosis. For individuals with localized disease, the 5-year survival rate is approximately 70%. When Ewing sarcoma has metastasized to distant parts of the body, the rate is closer to 30%. These statistics are general estimates and can vary based on individual circumstances.
Long-term follow-up care is necessary for survivors to monitor for any signs of cancer recurrence and to manage any late effects of treatment. The treatments used for Ewing sarcoma, particularly chemotherapy and radiation, can have long-term side effects that require ongoing care. Continued research into new and more targeted therapies offers hope for further improving the prognosis for individuals diagnosed with this rare cancer.