Role of chemotherapy in dedifferentiated liposarcoma of the retroperitoneum: defining the benefit and challenges of the standard.

Benefit from chemotherapy for well-differentiated/de-differentiated (WD/DD) liposarcomas has been reported to be minimal, however traditional response criteria may not adequately capture positive treatment effect. In this study, we evaluate benefit from first-line chemotherapy and characterize imaging response characteristics in patients with retroperitoneal (RP) WD/DD liposarcoma treated at The University of Texas MD Anderson Cancer Center. Response was assessed using RECIST (Response Evaluation Criteria in Solid Tumors) and an exploratory analysis of vascular response was characterized. Among 82 patients evaluable for response to first-line therapy, 31 patients received neoadjuvant chemotherapy for localized/locally advanced disease; 51 received chemotherapy for unresectable recurrent/metastatic disease. Median overall survival from the start of chemotherapy was 29 months (95% CI 24-40 months). Response rates by RECIST: partial response (PR) 21% (17/82), stable disease (SD) 40%, and progression (PD) 39%. All RECIST responses were in patients receiving combination chemotherapy. A qualitative vascular response was seen in 24 patients (31%). Combination chemotherapy yields a response rate of 24% and a clinical benefit rate (CR/PR/SD > 6 months) of 44%, higher than previously reported in DD liposarcoma. A higher percentage of patients experience a vascular response with chemotherapy that is not adequately captured by RECIST in these large heterogeneous tumors.