Radiation Therapy
Although small sarcomas can be treated with surgery alone, the majority of sarcomas are greater than five centimeters in size. These sarcomas are routinely managed by a combination of surgery and radiation therapy. Radiation therapy may be used before, during, and after surgery.
Irradiation sterilizes tumor cells, damaging their DNA so they are no longer able to divide and multiply. Tumor cells beyond the reach of surgery may be neutralized by irradiation.
In comparison to other tumors, the margin of normal tissue subjected to radiation in surgery for soft tissue sarcoma is larger. This is because sarcoma can spread along muscles and between them in ways that sometimes cannot be seen or felt. Microscopically sarcoma cells are discrete, but they can trickle out deceptively and be left behind after surgery. The further away from the tumor site, however, the less likely there are to be sarcoma cells. Radiation oncologists typically irradiate tissue five to 10 centimeters (approximately two inches) beyond where the tumor was located.
Brachytherapy
Brachytherapy, which involves delivering radiation therapy locally, can be administered in two different ways to treat soft tissue sarcoma. Memorial Sloan-Kettering has pioneered the use of brachytherapy for the treatment of soft-tissue sarcoma.
In one approach, during surgery, after the surgeon removes the tumor, special tubes called catheters are inserted into the tumor bed. After allowing the surgical wound to heal for five to six days, the radiation oncologist inserts radioactive seeds into each of the catheters. The seeds stay in place for several days (usually five days), delivering a high dose of radiotherapy to the site.
When the treatment is completed, both the radioactive seeds and the catheters are removed. A patient could finish the entire course of treatment within 10 to 14 days. In certain situations, brachytherapy may be administered for two to three days combined with external radiation for five weeks.
A second form of brachytherapy, called high-dose-rate intraoperative radiation therapy, is delivered entirely during surgery. After the surgeon removes the tumor, applicators are placed against the surface from which the tumor has just been removed. The applicators are attached to a radiotherapy machine that is programmed to send a high dose of radiotherapy directly to the site.
External-Beam Radiation Therapy
External-beam radiation therapy uses doses of radiation delivered from outside the body, focusing on the region of the tumor and surrounding tissues. After postoperative recovery, a course of external beam radiation therapy is usually given. This approach is most useful for the retroperitoneum (the area outside or behind the peritoneum, which is the tissue that lines the abdominal wall and covers most of the organs in the abdomen) and chest, where it is not feasible to leave catheters in place. It is typically a seven to eight week process in which the patient comes in five days a week as an outpatient, for a few minutes worth of radiation therapy at each visit. It can be given before or after surgery.
IMRT
Intensity modulated radiation therapy (IMRT), a new sophisticated computer-guided technique that allows safe delivery of much higher doses of radiation to the tumor while sparing the normal surrounding tissues, is now being used to treat soft tissue sarcoma before surgery. The goal is to use IMRT to shrink the tumor, making the surgery more successful and reducing the chance of recurrence. These tumors can sometimes be very close to the spine or major blood vessels, so this targeted therapy can provide benefit.