(P 210) A LONGITUDINAL ANALYSIS OF PROGNOSTIC FACTORS IN CHINESE PATIENTS WITH RETROPERITONEAL LIPOSARCOMA

Objective: The primary objective is to identify prognostic factors for retroperitoneal liposarcomas (RPLS). Secondary objectives include: 1. explore effects of neoadjuvant/adjuvant treatments on local recurrence free survival (LRFS) and overall survival (OS); 2. explore effects of post-local recurrence treatments on OS; 3. review use of palliative chemotherapy in recurrent RPLS.

Methods: This is a retrospective, longitudinal study of patients with RPLS treated between 2009 to 2021 at Prince of Wales Hospital - a tertiary referral sarcoma centre in Hong Kong. A total of 51 patients with RPLS were included in the analysis. Univariate and multivariate cox regression analyses were performed to identify factors predictive of local recurrence and OS.

Results: Median OS was 5.8 months in patients who did not undergo primary tumor resection, compared to 131.0 months in patients who had surgery (P < 0.001). Of the 43 out of 51 patients who underwent curative-intent primary tumor resection, 20 (47%) presented with well-differentiated, 21 (49%) with dedifferentiated, 1 (2%) with myxoid, and 1 (2%) with mixed histology. Multivariate analysis showed dedifferentiated (DDLPS) histology (P = 0.018) and R2 resection (P = 0.002) predicts poor prognosis in OS. Neoadjuvant chemotherapy (P < 0.001) is associated with higher risk of death in univariate analysis. 24 out of 37 (65%) patients had local recurrence after initial complete macroscopic resection, with median time to local recurrence of 30.5 months. After local recurrence, the median post-recurrence survival in patients who underwent re-excision was significantly longer (89.1 months) compared to those treated with palliative chemotherapy only (6.8 months) (P = 0.035). The median duration of use of palliative chemotherapy is 5 months with median survival of 10.4 months after chemotherapy initiation. Longer survival of up to 5 years is seen in patients who responded to eribulin.

Conclusion: Surgery remains the cornerstone of RPLS treatment with >20-fold improvement in median OS in patient who underwent primary tumor resection. DDLPS histologic subtype and R2 resection are negative prognostic factors for survival in RPLS. Neoadjuvant chemotherapy use may be associated with higher risk of death. Re-excision provides longer post-recurrence survival compared with palliative chemotherapy only. Eribulin may be a more efficacious agent for RPLS palliative treatment. Larger prospective randomized trials are needed to confirm these findings.

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