Ewings’ sarcoma is the second most frequent primary malignant bone cancer in patients younger than 20 years of age; up to a third of patients can be diagnosed before the age of ten. Although rare, boys have a slightly higher incidence than girls (55:45 male: female ratio). The cancer is more common among Caucasians than Asians or African Americans.
Most Ewings’ sarcomas occur in long bones sometimes flat bones of the axial skeleton are also affected. The most common sites include the pelvic bones, the long bones of the lower extremities, and the bones of the chest wall. The tumor often spreads to the lungs, and bone marrow, while spread to the lymph nodes, liver, or central nervous system are rare.
Patients with Ewings’ sarcoma complain of local pain of the affected bone, which is more at night. This is often dismissed or misdiagnosed as sports injury pain such as tendonitis. However, a palpable mass over the persistent pain area with no history of trauma, must raise suspicion in a patient in the 20’s age group, demanding imaging studies. MRI imaging can furnish details including local extent of the disease, intramedullary portion and the relation of the tumor to adjacent blood vessels and nerves. Additional symptoms arise depending on the site of the sarcoma.
A small proportion of Ewings sarcomas may arise outside the bone, from muscle and are known as extra-osseous Ewings sarcomas.
Biopsy provides a definitive diagnosis. Histological examination, as described by James Ewings in 1921, is characterized by monotonous sheets of small cells with round nuclei. However, to distinguish among other childhood tumors, namely rhabdomyosarcoma, and synovial sarcoma, molecular and genetic studies may be advised.
Imaging and biopsy results aid in staging of Ewings’ sarcoma. Even small tumors can easily reach nearby muscles and tendons. The tumor is considered localized only when imaging studies – X-rays, CT, MRI, PET, and bone scans do not show any evidence of spread or a bone marrow biopsy is not tumor positive. Survival rates for localized tumors are 70% compared to about 30% in case metastasis (spread) has occurred. Chemotherapy can reach distant sites and is effective for treatment in Ewing’s sarcoma. Earlier, surgical amputation of limb used to be the main form of treatment; however, this is now adopted for patients after initial chemotherapy or when the tumour recurs.
Initial chemotherapy followed by surgery /radiotherapy is followed by almost 12 months of chemotherapy in localized disease to cure these tumors.
Radiation plays a major role in the management of this tumor. Radiation is provided by external beam radiation therapy with chemotherapy. Patients who have inoperable tumors or advanced tumors are treated with radiation therapy alone for relief of symptoms. Conventional radiation therapy is administered over a course of 5-6weeks. Intraoperative radiation therapy consists of a single dose of radiation therapy delivered directly to the area of the tumor during surgery. The radiation oncologist present during surgery avoids sensitive normal structures, such as blood vessels and nerves, which can be moved away from the radiation beam.
Three-dimensional conformal radiation therapy precisely targets radiation to the areas where cancer cells may be located. Intensity modulated radiation therapy delivers precise specified doses of radiation to cancer cells. Radiation therapy also helps to prevent local and regional recurrences (cancer recurrence in the area of the primary tumor). Radiation is also given after surgery to eradicate evidence of tumor, and can also be followed by chemotherapy since radiation cannot reach distant spread of tumor.
Hence a multidisciplinary team of skilled oncosurgeons, radiation oncologists, and orthopedic surgeon specializing in bone cancers, and pathologists form the core team involved in the management for the optimal survival and quality of life in patients with Ewing’s sarcoma.