Radiation treatment of Ewing's sarcomaMedical editor Jan Peter Poulsen MD
Oslo University Hospital
Patients with Ewing's sarcoma are given postoperative radiation treatment for marginal or intralesional surgical margins. Radiation therapy may also be administered without previous surgery. Treatment is given in combination with chemotherapy.
The total treatment time for Ewing's sarcoma is 30-40 weeks and radiation treatment is given in week 14-17 for postoperative radiation treatment and in week 13-16 for inoperable tumors.
For metastases, radiation treatment is given for symptom relief. Total lung irradiation is administered 10 weeks after end of chemotherapy.
Many patients are children and the indication for radiation treatment must be determined by a risk/benefit analysis.
Ewing's sarcoma with:
- operable tumor
- after marginal surgery and not complete histological response
- after intralesional surgery
- inoperable tumor
- metastatic disease
- for inoperable bone metastasis
- lung metastasis
- pain relief from bone metastases
- Cure the disease
The target volume is + 3 cm for operated patient. If the patient has not been operated, the target volume of radiological tumor is + 2 cm.
|Target volume definitions from ICRU
(International Commission on Radiation Units and Measurements)
GTV (= Gross Tumor Volume)
|Palpable or visible/identifiable area of malignant growth. Involved lymph nodes are indicated by GTV-N, other metastases as GTV-M.
CTV (= Clinical Target Volume)
Clinical target volume
Tissue volume containing GTV and/or subclinical microscopic malignant disease. CTV = GTV + 3,0–4 cm lengthwise and + 1,5–2 cm i all other directions.
ITV (= Internal Target Volume)
Volume containing CTV and inner margin taking into account movement and revisions of CTV. This is the volume that should obtain the optimal dose.
PTV (= Planning Target Volume)
Geometric volume containing ITV and one set-up margin taking into account patient movement, variation in patient positioning, and field modeling.
PTV = CTV + 1,0 cm in all directions
Planning contour: Beams-Eye-View projection of PTV.
IM (= Inner margin) and SM (= Setup margin)
|IM and SM cannot be summed linearly. Total margin must be given specifically for different tumor localizations.
A CT dosage plan should be carried out and preferably multiple individual shaped fields. Immobilization might be necessary .
If possible, avoid treating the entire extremity to reduce the risk for delayed edema.
Radiation treatment is administered as photons and electrons.
Marginal and intralesional surgery
- Total dose is 42 Gy, given hyperfractionally 1.5 Gy twice daily, 5 days per week.
- Total dose is 54 Gy hyperfractionally (1.5 Gy twice daily), 5 days per week.
- Solitary bone metastasis (inoperable) should receive the same radiation treatment as a primary inoperable tumor.
- Total lung radiation (TLI) is given for lung metastases or after a lung metastasectomy. That is, 1.5 Gy x 10 Gy.
- Painful bone metastases are treated according to palliative guidelines, 8 Gy x 1 and 3 Gy x 10.
Acute radiation side effects occurs to a varying degree depending on radiation dosage and tolerance. The side effects vary according to the localization of the radiation field as some structures are more sensitive to radiation than others.
Acute radiation injury occurs during the radiation treatment period or shortly thereafter.
- Redness in the skin
- Open wounds
- Poor healing of skin transplant
Types of delayed damage depend on the location of the tumor and radiation dose. Delayed damage may be:
- Risk for secondary cancer
- Joint contractures
- Insufficiency fracture