Preliminary results of a randomized study of adjuvant radiation therapy in resectable adult retroperitoneal soft tissue sarcomas.

Between January 1980 and September 1985, 35 adult patients with resectable retroperitoneal soft tissue sarcomas were entered on a randomized trial comparing two forms of adjuvant radiation therapy. Fifteen patients received the experimental therapy consisting of intraoperative radiotherapy (IORT) to 20 Gy using high-energy electrons followed by low-dose (35 to 40 Gy) postoperative external beam irradiation. Twenty patients received standard therapy consisting of high-dose (50 to 55 Gy) postoperative external beam irradiation. With a minimum follow-up of 15 months, there is no significant difference in the actuarial disease-free survival (DFS) and overall survival (OS) comparing the two groups (median DFS, 34 months; median OS, 38 months). At 5 years follow-up, approximately 40% of patients are alive and 20% of patients remain disease-free. Although there is a trend towards an improvement in in-field local control in the experimental arm, the predominant pattern of failure in both groups was locoregional within the retroperitoneum and/or peritoneal cavity. Acute and late radiation enteritis were significantly reduced in the experimental group. However, four experimental patients developed late (greater than 6 months following treatment) peripheral neuropathy believed related to the use of IORT; all four recovered. We conclude that there is no difference in the therapeutic effectiveness of the combination of IORT and low-dose external beam radiation compared with conventional high-dose radiation as adjuvant treatment in retroperitoneal sarcomas, although the former appears to be less toxic. Newer combined modality treatment strategies are discussed to improve the prognosis in these patients.