The prognostic impact of dedifferentiation in retroperitoneal liposarcoma

BACKGROUND: A series of patients with well differentiated (WD)/dedifferentiated (DD) retroperitoneal liposarcoma (RLS) was studied to evaluate the prognostic value of the presence, extension, and grade of the DD component. METHODS: Among 148 patients with RLS who underwent surgery over 20 years, the authors retrieved data on patients who had localized WD/DD RLS. For the current analysis, patients were included only if they had primary disease or a first recurrence at their initial presentation. The DD component, when present, was graded according to National Federation of Centers in the Fight Against Cancer (FNCLCC) criteria, and the extension of the DD component was described as a percentage. Univariate and multivariate analyses were carried out for local recurrence-free survival (LRFS), event-free survival (EFS), and disease-specific survival (DSS). RESULTS: Of 93 patients who were identified, 36 patients (39%) had WD RLS, and 57 patients (61%) had DD RLS. The median follow-up was 71 months (range, 28-132 months). Seven patients (7.5%) developed distant metastases, including 5 patients who had DD RLS. The 5-year DSS rate was 42% in patients with DD RLS and 71.6% in patients with WD RLS (P = .018). The corresponding rates for LRFS were 22% and 43.3%, respectively (P = .007). The presence of the DD component and its FNCLCC grade were independent prognostic factors for DSS and LRFS. The administration of radiation therapy was associated independently with better LRFS. CONCLUSIONS: Patients with high-grade DD RLS had a worse prognosis in terms of both DSS and LRFS. The extension of the DD component and its mitotic index were relevant for EFS. The results indicated that radiation therapy may improve LRFS. These data may help stratify the risk of recurrence for patients with RLS. Clinical studies on new multimodality approaches are warranted.