(P 300) RECURRENCES AFTER PRIMARY RPS SURGERY IN A HIGH-VOLUME SARCOMA CENTER: A RETROSPECTIVE ANALYSIS ON 402 PATIENTS

Objective: The objective of this study was to evaluate the treatment strategies and outcomes for recurrences of primary retroperitoneal sarcomas (RPS) in a high-volume sarcoma center.

Methods: We conducted a retrospective review of all consecutive patients who underwent surgery for RPS at our tertiary care center between 1994 and 2024. Recurrences were defined as local if they occurred at the surgical site or within the peritoneum, and distant otherwise. Survival outcomes were estimated using Kaplan-Meier methods from the date of diagnosis and compared using the log-rank test. A Cox proportional hazards model and competing risk analysis were also employed.

Results: A total of 402 patients were included, with a median age of 60 years at diagnosis. Histologic subtypes included 30% well-differentiated liposarcoma (WDLPS), 49% dedifferentiated liposarcoma (DDLPS), 16% leiomyosarcoma (LMS) and other (12% high-grade, 4% low-grade). Preoperative chemotherapy and radiotherapy were administered in 14% and 11% of patients, respectively. Postoperative chemotherapy and/or radiotherapy was given to 17% of patients. After a median follow-up of 90 [79–102] months, the median overall survival (OS) was 16 [11–not reached] years and the median disease-free survival (DFS) was 7,9 [7,25–9,25] years. In the competing risk analysis stratified by histologic subtype, LMS was associated with the highest risk of distant recurrence, and DDLPS with the highest risk of local recurrence.184 patients (46%) experienced recurrence. Among the 137 patients with local recurrence, 30% underwent surgery, 48% received chemotherapy, 23% radiotherapy and the median OS was 32 [23–58] months. Among the 80 patients with distant recurrence 25% were treated surgically, 48% with chemotherapy, 31% with radiotherapy and the median OS was 29 [22–53] months.

Conclusion: This study provides one of the largest single-center analyses of recurrence after primary RPS surgery. While primary surgery achieves good initial disease control, both local and distant recurrences remain associated with poor survival outcomes.