Lack of survival benefit following adjuvant radiation in patients with retroperitoneal sarcoma: A SEER analysis

Background: The benefit of radiation therapy (RT) among patients with retroperitoneal sarcoma (RPS) is controversial. We performed a retrospective analysis of the effect of RT on survival among RPS patients using a nationwide cancer registry. Methods: Utilizing data from the Surveillance, Epidemiology, and End Results (SEER) database, we identified 2308 cases of RPS from 1988 to 2004. We excluded 773 cases for age < 18, identification by autopsy only, absence of histologic confirmation, presence of metastatic disease, or lack of surgical intervention. Overall survival (OS) and disease-specific survival (DSS) were estimated using the Kaplan-Meier method. Multivariate analysis was performed using a Cox proportional hazards model, adjusting for significant covariables. Results: Among 1535 patients who met entry criteria, RT was administered to 373 patients (24.3%). The majority of RT (n = 300, 80.4%) was administered postoperatively. Median OS was 60 and 60 mo, respectively, for patients receiving and not receiving RT (P = 0.59). Median DSS was 86 and 117 mo, respectively, for patients receiving and not receiving RT (P = 0.84). On multivariate analysis, younger age, female gender, low and intermediate histologic grade, liposarcoma histology, tumor size 5-10 cm, and completeness of resection all independently predicted better OS and DSS, while RT did not (HR for OS with RT 0.92, 95% CI 0.78-1.09 and HR for DSS with RT 0.96, 95% CI 0.78-1.17). On subgroup analysis by histology, patients with malignant fibrous histiocytoma (MFH) receiving RT demonstrated statistically improved OS (P = 0.002) and DSS (P = 0.01), respectively. Conclusions: With the possible exception of MFH, postoperative RT offers no survival benefit in RPS. Further studies are necessary to determine if the selective application of RT is indicated.