Preoperative and postoperative irradiation of soft tissue sarcomas: effect of radiation field size.

For the treatment of soft tissue sarcomas it has frequently been staged but not quantitatively demonstrated, that the volume irradiated is smaller when irradiation is given preoperatively as compared to postoperatively. In this study the field size used for preoperative irradiation was compared with that necessary in the same patient had the radiation been given postoperatively. Twenty-six patients with soft tissue sarcomas of the extremity, groin, and shoulder girdle who had received preoperative irradiation were resimulated following surgery to determine the size of the postoperative field. The simulation was performed by a physician not involved in the preoperative treatment planning. Preoperatively a radial margin of 5 cm around the tumor was used for low and intermediate grade and 7 cm for high grade sarcomas. Postoperatively the same margins were used but around the surgical field. Twelve patients underwent a wide resection and 14 patients a resection followed by vascularized tissue transfer to the surgical bed. The median follow-up was 22 months (range 13-46). No local recurrences and two cases of distant metastasis were observed. Independently of surgical procedure and tumor grade, the size of the preoperative radiation field and number of joints included in the field were significantly smaller than that of postoperative radiation (p less than 0.001). In two patients preoperatively and four patients postoperatively, the radiation field involved the whole circumference of the limb. Provided that equivalent radiation time-dose-fraction parameters are used and that the complication rate is proportional to the radiation field size, late complications may be less after preoperative irradiation than after post-operative irradiation.