Radiation Therapy
by Carol D. Morris, MD, MS
Radiation therapy is administered by a radiation oncologist. The purpose of radiation is to improve local tumor control by killing residual microscopic disease. Typical radiation doses vary from 45 Gy to 65 Gy.
In a prospective randomized trial from NCI, 91 patients with high grade tumors were randomized to surgery alone or surgery with post-operative external beam radiation therapy, XRT (Ref. 48). Patients in the surgery alone group experience 20% local recurrence rates compared to 0% for the surgery plus XRT group. For both groups, there was no difference in overall survival. In general, patients treated with adequate limb-sparing surgery supplemented with radiation have a likelihood of experiencing over 85% local control.
There are several different ways to administer radiation. The most commonly used form of radiation is external beam radiation which can be given pre-operatively, intra-operatively, post-operatively, or in some combination. Each has advantages and disadvantages, see Table 3. For tumors that are in contact with major nerves and blood vessels, pre-operative radiation can potentially shrink the tumor, making limb-sparing surgery possible or easier. The main disadvantage to pre-operative radiation is its association with post-operative wound complications (Refs. 10 and 35). Post-operative radiation is probably the most commonly used modality. Typically pre- and post-operative radiation is administered over a 5 week period. Intra-operative has the advantage of delivering a large dose of radiation directly to an area of concern while sparing nearby organs such as the bowel or bladder. It is particularly useful for treating large retroperitoneal sarcomas in which it is difficult to obtain local tumor control (Ref. 43).
| Delivery Method | Advantages | Disadvantages |
|---|---|---|
| Pre-operative |
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| Intra-operative |
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| Postoperative |
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Another means of administering radiation is a technique called brachytherapy. After the surgeon has removed the tumor, a radiation oncologist then places empty catheters in the operative bed. Once the wound is starting to heal (approximately 5 days after surgery), the catheters are filled with radioactive material which sits in the surgical bed for 5 days. This allows for high doses of radiation over a short period of time obviating the need to travel daily for radiation treatments over several weeks.
In a prospective randomized trial conducted at the Memorial Sloan-Kettering Cancer Center, 164 patients with extremity or superficial axial sarcomas were randomized to surgery alone versus surgery plus brachytherapy (Ref. 38). For patients with high grade tumors, the 5-year local control rate was 89% in the brachytherapy group, compared to 66% in the surgery only group. There was no difference in overall survival between the groups. A retrospective review from the same institution examined small (<5cm) high grade sarcomas treated with brachytherapy (Ref. 37). There was no advantage in local control or overall survival for this subgroup of patients.
Unfortunately radiation does have well known side effects. Problems with wound healing have already been described above. Problems also include scarring of the tissue resulting in firm, stiff muscles as well as skin discoloration have also been well described. The most serious complication arising from radiation is the development of a second cancer within the radiated field (Refs. 8, 29, and 32) This is called a post-radiation or radiation-induced sarcoma. Radiation-induced sarcomas are rare and occur in less than 5% of long-term survivors.
Source: "Malignant Fibrous Histiocytoma (MFH)"
by Carol D. Morris, MD, MS.
References can be found here.
V2N2 ESUN Copyright © 2005 Liddy Shriver Sarcoma Initiative.