(P 339) QUALITY OF SURGERY AND OUTCOME FOR GIANT RETROPERITONEAL LIPOSARCOMA TREATED WITHIN SEMI-ABDOMINAL EN BLOC RESECTION USING VASCULAR PRIORITY CENTRAL APPROACH-A RETROSPECTIVE COHORT

Objective: Retroperitoneal liposarcoma (RPLS) is defined as an aggressive malignant tumor for which adjuvant modalities have not shown increased efficacy compared with surgery, due to the giant tumor burden and characteristics of invasion. The optimal treatment strategy and standardized surgical procedures for giant RPLS are still unknown. In this study, we aimed to evaluate the surgery quality and clinical outcomes of giant RPLS patients with semi-abdominal En Bloc resection using a vascular priority central approach, to determine their potential prognostic and therapeutic utility.

Methods: Retrospective medical record review of a cohort of 132 patients who presented to the Zhongshan Hospital, Fudan University during the period from March 2010 to September 2021. Median follow-up was 37.4 months (IQR, 21.5-71.2 months). Inclusion criteria were confirmed diagnosis of primary or secondary RPLS, with an intermediate or high risk of relapse; no evidence of residual disease after surgery; older than 26 years; and no prior malignancies or concurrent severe/uncontrolled medical conditions. Data were analyzed during the period from September 2022 to May 2023. Demographic and clinical factors were evaluated to assess the clinical course, patterns of recurrence, and survival outcomes for patients with RPLS. Univariate and multivariate Cox proportional hazards models were used to correlate disease-specific overall survival (OS), disease-free survival (DFS), and post-relapse OS with potential prognostic indicators.

Results: 132 patients with localized RPLS who underwent surgical resection with semi-abdominal En Bloc resection using vascular priority central approach formed the study population, and their clinical features were used for subsequent outcomes analysis (Figure 1). The median age at diagnosis was 55 years (range, 27-84 years). The majority of patients were male (69 patients [52.3%]). The 5-year disease-specific OS after semi-abdominal En Bloc resection was 62.5%. The median time to OS was 80.5 months (IQR, 21.5-71.2 months), and the median time to post-relapse OS was 24.3 months (IQR, 11.9-36.8 months). The median diameter was 21 cm (IQR, 4.5-47cm) and the median operation time was 5.3 hours (IQR, 2-12 hours). The median number of organs resected was 5 (IQR, 3-8) and the median hospitalization days were 30 days. Severe postoperative adverse events (Clavien-Dindo>3) occurred in 31 patients (23.48%) and none patients died within 30 days. Left-sided RPLS patients receiving semi-abdominal En Bloc resection, longer operation time, more resected organs and blood loss indicated higher operative risk (Figure 2). No impact of postoperative adverse events was found associated with OS, DFS, and post-relapse OS. Significant and independent predictors of OS and DFS were transfusion requirement and FNCLCC grade (Figure 3).

Conclusion: A radical and standardized surgical procedure using a vascular priority central approach for giant RPLS is safe when carried out at a high-flow, experienced specialist sarcoma center. Multivisceral resections should be carefully considered and discussed on an individual basis in RPLS-specific MDT and weighed against anticipated disease biology.