Ewing Sarcoma, from the CureRays guide library.

Ewing sarcoma is a rare bone and soft-tissue cancer mostly in children and young adults; it is very sensitive to chemotherapy and radiation, which work together with surgery to cure many patients.

What it is.

Ewing sarcoma is a rare cancer that usually starts in bone — often the pelvis, legs, arms, ribs, or spine — but can also begin in the soft tissues around bone. It mostly affects children, teenagers, and young adults. Ewing sarcoma is driven by a specific genetic change inside the tumor cells (most often a fusion involving the EWSR1 gene), which helps doctors confirm the diagnosis. Common warning signs are pain and swelling near the affected bone, sometimes mistaken at first for a sports injury, and occasionally fever. Because Ewing sarcoma can spread early, even when it looks localized, treatment always begins with chemotherapy that travels throughout the body, followed by local treatment of the main tumor with surgery, radiation, or both. Ewing sarcoma is one of the more radiation-sensitive solid tumors, which gives radiation an especially important role. Care is delivered by a specialized pediatric and sarcoma team, and many patients are cured, particularly when the cancer has not spread to distant sites.

How radiation treats it.

Radiation uses focused high-energy x-rays — or, in some centers, proton beams — to damage the DNA inside cancer cells so they can no longer grow and divide. Ewing sarcoma is one of the more radiation-sensitive solid tumors, which means radiation can be very effective at controlling the main tumor and sites of spread. After chemotherapy shrinks the tumor, radiation is often used as the local treatment when surgery would remove too much bone or cause major loss of function, or when some tumor remains after surgery. Because many patients are children and young adults, the team plans treatment with great care to protect growing bones, nearby organs, and long-term health, sometimes using proton therapy to reduce the dose to healthy tissue. Treatments are painless and given over a series of short daily sessions. Side effects depend on the area treated and are managed closely by the pediatric and sarcoma team.

The ways we can treat it.

Definitive radiation. For tumors in places that are hard to remove (such as parts of the pelvis or spine), focused radiation can be the main local treatment, taking advantage of Ewing sarcoma's strong sensitivity to radiation.

Post-surgery radiation. Radiation after surgery lowers the chance of return when margins are close or when the tumor responded less well to chemotherapy.

Whole-lung radiation. When the cancer has spread to the lungs, gentle radiation to both lungs can help control disease alongside chemotherapy.

Proton therapy. In children and young adults, proton beams can deliver radiation to the tumor while reducing dose to growing bones and nearby organs, lowering long-term side effects.

Questions we hear often.

Why does chemotherapy come first? Ewing sarcoma can spread early, even when scans look clear. Starting with chemotherapy treats any hidden cancer throughout the body and shrinks the main tumor, which makes the later local treatment with surgery or radiation more effective.

Surgery or radiation — which is better? Both can control the main tumor. The choice depends on where the tumor is, how big it is, whether it can be fully removed, and how it affects function. For tumors in hard-to-reach places like parts of the pelvis or spine, radiation is often the main local treatment because Ewing sarcoma responds so well to it.

Can Ewing sarcoma be cured? Yes, many patients are cured, especially when the cancer has not spread to distant sites. Even when it has spread, treatment can be effective. Care from an experienced pediatric and sarcoma team gives the best chance.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.