Retroperitoneal dedifferentiated liposarcoma: Analysis of 61 cases from a large institution

Background: To describe the clinical features of retroperitoneal dedifferentiated liposarcoma (RP DDLS) and further evaluate the prognostic factors.Methods: The clinicopathological variables and treatment strategies of 61 RP DDLS patients who underwent surgical resections at a single institution between September 2005 and September 2016 were reviewed.Kaplan-Meier and Cox regression methods were conducted for survival analyses.Results: The average patients' age was 52 years (range, 27-81), and there was almost no gender predilection (30 males vs. 31 females).51 (83.6%) patients got gross tumor resections (R0/R1 resection), and the median tumor size was 19 cm (range, 4.3-50 cm).39(63.9%)patients were with intermediate-grade sarcoma and 22(36.1%)were with high-grade sarcoma.The median intraoperative blood loss was 400 ml (range, 50-2700ml).19 (31.1%) patients presented multifocal diseases.Tumors were removed intactly in 42 (68.9%)patients.In order to obtain gross tumor resections, 33 (54.1%) of the patients underwent excisions of at least one adjacent organ, of which kidney (n=21, 63.6%) was the most common one.6 (9.8%) patients developed distant metastases during follow-up.The overall 5-year progression-free survival (PFS) rate was 3.7%, with the median PFS of 19 months.The 5-year overall survival (OS) rate was 43.5%, with the median OS of 58 months.Updating to November 2017, 30 (49.2%) patients remained alive.The median follow-up time was 49 months.Multivariate analysis using Cox proportional hazards model revealed that tumor grade, blood loss, resection extent, and tumor integrity were independently associated with OS (p=0.032,p=0.018, p=0.020, p=0.005, respectively).Tumor grade, tumor integrity and multifocality were significant predictors for PFS (p=0.013,p=0.080, p=0.009, p=0.028, respectively).Conclusion: Intermediate-grade histology, intraoperative blood loss < 400 ml, complete tumor resection, and tumor integrity were independently associated with better OS.Intermediate-grade histology, tumor integrity and unifocal disease independently predicted favorable PFS.