Histologic type predicts survival in patients with retroperitoneal soft tissue sarcoma

Background: Histologic grade, completeness of resection, and presence of metastases are traditionally regarded as the primary factors in predicting survival for retroperitoneal soft tissue sarcoma (RPSTS). We sought to examine the importance of histologic type as a prognostic factor among patients with RPSTS. Methods: We identified 2337 cases of RPSTS in the Surveillance, Epidemiology, and End Results (SEER) database from 1988 to 2004. After excluding 273 cases of age <18, identification by autopsy only, or absence of histologic confirmation, we arrived at a final study cohort of 2064 patients. 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 age, gender, race, histologic type, histologic grade, tumor size, extent of resection, and SEER summary stage. Results: Among 33 histologic types, leiomyosarcoma (28.7%), well-differentiated/ dedifferentiated liposarcoma (20.3%), liposarcoma not otherwise specified (NOS) (11.9%), malignant fibrous histiocytoma (MFH-11.0%), and sarcoma NOS (10.7%) were the most prevalent. Grade distribution was low, 24.2%; intermediate, 16%; high 34.3%, and unknown, 25.5%. Surgery was performed in 85.8%, and radiotherapy was administered to 22.8%. With a median follow-up of 38 mo, median OS was 78, 35, 25, 18, and 10 mo for liposarcoma, leiomyosarcoma, other histologies, MFH, and sarcoma NOS, respectively (P < 0.0001). Median DSS was 120, 53, not reached, 30, and 13 mo for liposarcoma, leiomyosarcoma, other histologies, MFH, and sarcoma NOS, respectively (P < 0.0001). On multivariate analysis, histologic type was associated with statistically significant differences in both OS and DSS. Conclusions: Histologic type is an important predictor of survival in RPSTS.