(P 513) THE IMPACT OF MARGIN STATUS ON THE ONCOLOGIC OUTCOMES OF SURGICALLY TREATED DEDIFFERENTIATED LIPOSARCOMA OF THE EXTREMITIES

Objective: Dedifferentiated liposarcoma (DDLPS) is an aggressive variant of liposarcoma that can arise within an atypical lipomatous tumor (ALT). The primary goal of treatment for DDLPS is wide margin resection, but there is sparse data to suggest whether the low-grade portion surrounding DDLPS also necessitates wide margin resection for optimal local control. We aimed to investigate the importance of surgical marginal location with respect to DDLPS and ALT tumor portions. The behavior of ALT/DDLPS at the margin can be rather unique in its ability to insinuate itself between tissue planes. This makes the achievement of a truly “wide” margin a difficult, if not impossible endeavor, in limb salvage surgery. This study aims to evaluate the oncologic outcomes of DDLPS with respect to the margins achieved at the time of surgical resection.

Methods: This retrospective institutional cohort study included all patients treated surgically for histologically confirmed DDLPS from 2007 to 2019. Patient and tumor demographics and oncologic outcomes were collected. Exclusion criteria included patients with less than two years of follow-up, intraperitoneal/retroperitoneal or head/neck liposarcomas, or age younger than 18 years. Pathology slides were re-reviewed by a surgical pathologist specializing in soft-tissue sarcoma. Margin status was categorized into one of the following categories as described by Enneking in the surgical staging system: wide (R0), marginal (R1) and intralesional (R2). These descriptors were applied to both the DDLPS and the ALT portions of the tumor. All patients were determined as either “wide throughout” or “wide on DDLPS, marginal on ALT”. Statistical analysis for patient outcome and margin status was carried out using chi-square tests for each patient outcome.

Results: 22 patients underwent oncologic resection for extremity DDLPS. 14 (63.6%) patients had surgical margins that were defined as wide on DDLPS/marginal on ALT, and 6 (27.3%) patients had surgical margins wide throughout, and 2 were unable to be determined (Table 1). The overall rate of local control was 90.9 % (20 of 22). 2 patients with surgical margins wide on DDLPS/marginal on ALT developed local recurrence compared with no patients with margins wide throughout (p = .53)(Table 2). 6 patients with surgical margins wide on DDLPS/marginal on ALT developed metastases compared to 1 patient with margins wide throughout (p = .31).

Conclusion: The surgical goal in DDLPS resection, as with other sarcomas, is a wide surgical resection. The data presented here do not alter that. However, this may not be feasible in many limb sparing surgeries. Our data indicate that wide compared with marginal resection of the surrounding low-grade portion did not appear to influence local recurrence, development of metastatic disease, or death from disease. However, due to the small size of this cohort, further investigation and discussion of margin importance is necessary. This study lays the foundation for future larger scale collaborative efforts to further determine the importance of margin acquisition as it relates to the ALT component of DDLPS.