Radiation Therapy
Although small sarcomas can be treated with surgery alone, the majority of sarcomas are greater than five centimeters in size and, thus, are managed by a combination of surgery and radiation therapy. Radiation therapy may be used before, during, or after surgery.
When used in combination with surgery, radiation therapy may reduce the chance of recurrence. Alternately, radiation may be used before surgery to shrink the tumor and thereby increase the space between the tumor and vital structures and organs, helping to improve the chance that the surgeon will remove all of the tumor cells. Radiation sterilizes tumor cells, damaging their DNA so they are no longer able to divide and multiply. This treatment can neutralize tumor cells beyond the reach of surgery.
In comparison to other tumors, soft tissue sarcoma requires that a larger margin of normal tissue be subjected to radiation. This is because sarcoma can spread along and between muscles in ways that sometimes cannot be detected. 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 deliver radiation to tissue five centimeters (approximately two inches) beyond where the tumor was located.
External-Beam Radiation Therapy
In external-beam radiation therapy, doses of radiation are delivered to the tumor area from outside the body. This approach is most useful when it is not feasible to leave catheters in place, as for tumors located in the retroperitoneum (the tissue that lines the abdominal wall and covers most of the organs in the abdomen) and the chest. Therapy with external-beam radiation therapy typically takes place over the course of seven to eight weeks, with the patient coming in five days a week for treatments that are several minutes long.
IMRT
Intensity-modulated radiation therapy (IMRT) is a sophisticated computer-guided technique that allows for safe delivery of much higher doses of radiation to the tumor than traditional radiation therapy while sparing the normal surrounding tissues. IMRT has become the standard radiation therapy used to treat soft tissue sarcoma because it reduces the risk of exposing bones to radiation, thereby reducing the risk of fracture after treatment.
IMRT can be used to treat most soft tissue sarcomas in the body, but it is best reserved for cases in which protection of important organs from radiation exposure is particularly important. Another added benefit of IMRT is its improved distribution of radiation throughout a large treatment area, which can be effective for treating tumors located in the thigh or retroperitoneal sarcomas.
A recent publication demonstrated the efficacy of IMRT in terms of local tumor control of soft tissue sarcomas in the extremities with a low risk of complications. The study, conducted by Memorial Sloan-Kettering investigators, found that using IMRT for the treatment of soft tissue sarcomas located in the arms or legs provides excellent tumor control. This suggests that the precision with which IMRT distributes the radiation dose has a beneficiary effect in sparing normal tissue and improving tumor response.
IGRT
Today, using a form of IMRT known as image-guided radiation therapy (IGRT), radiation oncologists are able to verify the exact location of a soft tissue sarcoma tumor prior to the delivery of radiotherapy or even during a treatment. This technique can help reduce the margin of healthy tissue exposed to radiation to five millimeters and, in certain cases, to as little as one or two millimeters. Because some soft tissue sarcoma tumors are located very close to the spine or major blood vessels, targeted therapy can provide substantial benefit in these cases.
Brachytherapy
Pioneered by Memorial Sloan-Kettering doctors for the treatment of sarcoma, brachytherapy involves delivering radiation therapy locally. It can be administered in one of two different ways to treat soft tissue sarcoma.
In one approach, which takes place during surgery, after the surgeon has removed the tumor, special tubes called catheters are inserted into the tumor bed. Once the surgical wound has healed (usually five to six days), the radiation oncologist inserts radioactive seeds into each of the catheters, which deliver a high dose of radiotherapy to the site.
When the treatment is complete (usually about five days after the radioactive seeds have been inserted), both the seeds and the catheters are removed. The entire course of treatment lasts from ten to 14 days. In certain situations, this form of 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 tumor bed. The applicators are attached to a radiotherapy machine that is programmed to send a high dose of radiotherapy directly to the site.