E438: Factors Associated with Recurrence in Dedifferentiated Retroperitoneal Liposarcoma: Analysis at a Reference Center

Retroperitoneal liposarcoma (RPLS) is the most common malignant tumor in retroperitoneal soft tissues and is classified based on the amount of lipid content within cells, mucoid lipids, and the degree of cell differentiation. These tumors are categorized into well-differentiated, myxoid/ round cell, pleomorphic, and dedifferentiated types. Dedifferentiated liposarcoma refers to a condition in which both well-differentiated and poorly differentiated liposarcoma, along with non-lipomatous sarcoma, coexist within a single tumor. It Carries an adverse prognosis due to a high local recurrence and distant metastases compared to other  sarcoma subtypes, and histological diagnosis can be challenging.

 

Methods: We conducted a retrospective analysis of medical records of DDLPS patients, analyzing clinical and pathological variables associated with disease recurrence, including, tumor size, degree of differentiation, location, vascular invasion, treatment, and resection margins.

Results:

We analyzed 95 cases diagnosed with RTP liposarcoma between January 2008 and December 2018, with 50 of them corresponding to dedifferentiated liposarcoma (DDLPS). Among these 50 DDLPS cases, 28 (56%) were male. The mean age was 54.30 years (±13.34), and the mean tumor size was 29.28 cm (±11.64). The most common symptom was an abdominal tumor. The majority of patients had locally advanced disease, with 46 (92%) at stage IIIB.  Multivisceral resection was performed in 54% of cases, with the kidney (46.8%) being the most frequently resected organ, followed by the colon (38.9%) and the spleen (10.5%). Postoperative morbidity occurred in 12% of cases (6 patients), and mortality was 5.3% (2 cases). During the follow-up of this patient group, recurrences occurred in 33 patients (66%), with 23 patients experiencing one recurrence, 6 patients having two recurrences, and 4 patients having more than three recurrences. Distant recurrence was observed in 5% of patients (2 patients). Multifocal primary tumors were found in 12 patients (31.6%), and sarcomatosis at initial diagnosis or recurrence was observed in 3 patients (7.9%). Vascular invasion (p< 0.05) and tumor grade (p=0.02) were identified as factors associated with recurrence.

Conclusions: Our study highlights the significance of vascular invasion and tumor grade as significant prognostic factors in the recurrence of dedifferentiated retroperitoneal liposarcoma. These findings may aid in identifying patients at higher risk of recurrence and inform clinical decision-making to improve outcomes in the management of this disease.