Resectable Well-Differentiated versus Dedifferentiated Liposarcomas: Two Different Diseases Possibly Requiring Different Treatment Approaches

Abstract

Division of retroperitoneal liposarcoma (RPLS) into well-differentiated (WD) and dedifferentiated (DD) subtypes is established; however, WD and DD are usually treated similarly. We hypothesized that WD and DD have distinct biological behaviors mandating different treatments. A prospective sarcoma database identified all primary/recurrent RPLS treated between 1996 and 2007: 77 DD (52%) and 58 WD (39.2%) patients were analyzed for recurrence rate, recurrence free survival (RFS), and overall survival (OS). At presentation, WD were mostly primary whereas DD were mostly recurrent (75.9% versus 58.4%; p = 0.04). A significant proportion of DD (37.7%) received chemotherapy compared to WD (1.7%; p < 0.0001). Multivisceral resection was more common in DD versus WD (45.5% versus 31%; p = 0.01). Gross total resection rates were equivalent (WD: 86.2%; DD: 85.7%). Overall and local recurrence were higher in DD versus WD (82.2% versus 50% and 71.2% versus 46.3%; p < 0.0001). Only 3.7% WD recurred as high grade metastatic disease. Median time to recurrence was 55.5 months in WD versus 13.5 months in DD (p < 0.0001). RFS and OS (1, 2, and 5 year) were higher in WD than DD (80.3% versus 55.9%; 65.1% versus 34.1%; 41.9% versus 7.8%; p < 0.0001) and (98% versus 88.1%; 95.6% versus 71.9%; 92.1% versus 36.5%; p < 0.0001) respectively. WD and DD have distinct biological behaviors. Gross total resection is achievable in most WD; unlike DD, high-grade recurrence is uncommon. Treatment should therefore reflect these biologic differences by maximizing survivorship while avoiding unnecessarily extensive multivisceral resection. The biological behaviors of well-differentiated and dedifferentiated liposarcomas differ significantly. This article presents outcomes of two different surgical approaches that were implemented at the UTMDACC, treating these tumors as different disease entities.