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Radiation treatment for soft tissue sarcoma in extremity


Medical editor Jan Peter Poulsen MD
Oncologist
Oslo University Hospital

General

Radiation treatment for high-grade malignant soft tissue sarcomas (grade III and IV) is administered to optimize local tumor control.

Some patients with high-grade malignant soft tissue sarcoma follow a protocol under testing (SSG XX) with hyperfractionated radiation treatment in addition to chemotherapy.

In some cases of low-grade malignant soft tissue sarcoma (grade I and II), radiation treatment is administered when a possible recurrence will cause a mutilating operation, for example amputation.

Palliative radiation therapy is administered to reduce symptoms from inoperable metastases.

Indications

Radiation treatment for soft tissue sarcoma is assessed on an individual basis:

  • For inadequate surgery, marginal or intralesional operation, independent tumor depth, where reoperation is not possible
  • For deep extramuscular and intramuscular tumors > 5 cm, independent of surgical margins (also for wide margins)
  • After surgery for local relapse
  • After initial surgery at non-sarcoma center, regardless of margin
  • To avoid a mutilating operation
  • For symptom-causing metastases

Goal

  • Cure the disease
  • Palliation

Definitions

Target volume

 

 

 

Target volume definitions from ICRU
(International Commission on Radiation Units and Measurements)

GTV (= Gross Tumor Volume)

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)

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)

Planning 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.

Preparation

For postoperative radiation treatment, the surgeon should participate in field determination.

Radiation treatment is administered most often after CT-dosage planning where one takes into account tumor volume, surgical and histological margins, and risk organs with emphasis on toxicity.


Implementation

Normal dosage is 2 Gy x 25 for patients operated with wide margins. Patients operated intralesionally are given 2 Gy x 5 as extra boost to a limited area.

Patients in the high risk group

The high-risk group of subcutaneous or deep tumors, narrow margins and deep tumors despite margins, are given 1.8 Gy x 2 x 10 days, total 36 Gy after 3rd cycle of chemotherapy.

Intralesionally operated patients are given 1.8 Gy x 2 daily x 12.5 days, total 45 Gy radiation treatment after 3rd cycle of chemotherapy.

Patients with tumor of any size, as measured on MRI, where surgery will lead to risk for intralesional margin are treated with 1.8 Gy x 2 daily x 10 days, total of 36 Gy after third cycle with chemotherapy before operation.

Low-grade malignant soft tissue sarcoma

For low-grade malignant soft tissue sarcoma when possible relapse will lead to mutilating surgery, 2 Gy x 25 is administered.

Palliative radiation treatment

For palliative radiation treatment, 3 Gy x 10-13 is administered.


Follow-up

When radiation therapy is administered in combination with chemotherapy, both acute and delayed side effects will increase.

The two most used chemotherapies for these diseases, doxorubicin and ifosfamide, both increase the effect of radiation treatment; they are "radiosensitizers." The magnitude of the increase is in not exactly known but the radiation dose must be drastically reduced (about 10%) to avoid prominent side effects when these two treatment modes are combined.

Acute radiation damage occurs to a varying degree, depending on radiation dose and the patient's tolerance. They occur during the radiation treatment period or a short time after. 

  • skin redness
  • blisters
  • open wounds
  • lack of healing of skin transplant
  • pain

Radiation damage varies for different localizations. Some structures are more sensitive to radiation than others. Radiation damage is graded according to a scheme from less serious to serious radiation damage.

Delayed reaction

Delayed reactions following radiation treatment are graded similarly to acute side effects. They occur months to years after concluded irradiation. The type of delayed reaction is dependent on the localization of the tumor and radiation dosage. Some delayed reactions may be:

  • Fibrosis
  • Risk of secondary cancer
  • Joint contractures
  • Osteoporosis
  • Pathologic fracture

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