Treatment Option Overview
In general, radiation is indicated for patients with inadequate surgical margins and for larger, high-grade tumors.[12,13] This is particularly important in high-grade tumors with tumor margins smaller than 1 cm.[14,15]; [Level of evidence: 3iiDiv] With combined surgery and radiation therapy, local control of the primary tumor can be achieved in more than 80% of patients.[17,18] Preoperative radiation therapy has been associated with excellent local control rates.[19,20,21] This approach has the advantage of treating smaller tissue volumes because it does not necessitate treating a postsurgical bed; it also has the advantage of somewhat lower radiation doses because relative hypoxia from surgical disruption of vasculature and scarring is not present. Preoperative radiation therapy has been associated with an increased rate of wound complications in adults, primarily in lower extremity tumors, but the degree of this is questionable. Conversely, preoperative radiation therapy may lead to less fibrosis than with postoperative approaches, perhaps due to the smaller treatment volume and dose. Brachytherapy and intraoperative radiation may be applicable in select situations.[18,24,25]; [Level of evidence: 3iiiDii] In the recently closed COG-ARST0332 trial, preoperative radiation therapy was recommended for patients who presented with unresected tumor. The use of postoperative radiation therapy for patients who presented following primary resection was dependent on the tumor size, grade, and margin status.
Retroperitoneal sarcomas are a special issue since radiosensitivity of the bowel to injury makes postoperative radiation therapy less desirable. Reasons for this include the postoperative adhesions and bowel immobility that increase the risk of damage from any given radiation dose. This is in contrast to the preoperative approach in which the tumor often displaces bowel outside of the radiation field, and any exposed bowel is more mobile, which decreases exposure to specific bowel segments.
Radiation volume and dose depend on all patient, tumor, and surgical variables as noted above. Considerations include patient age and growth potential, the ability to avoid critical organs, epiphyseal plates, and lymphatics (but not the neurovascular bundles that are relatively radiation tolerant), and the functional/cosmetic outcome. Radiation margins are typically 2 cm to 4 cm longitudinally, and encompassing fascial planes axially. Radiation doses are typically 45 Gy to 50 Gy preoperatively, with consideration for postoperative boost of 10 Gy to 20 Gy if resection margins are microscopically or grossly positive, or planned brachytherapy if the resection is predicted to be subtotal. However, data documenting the efficacy of a postoperative boost are lacking. The postoperative radiation dose is 55 Gy to 60 Gy, or rarely, higher in the situation where unresectable gross residual disease exists.