Incidence and Adverse Prognostic Implications of Histopathologic Organ Invasion in Primary Retroperitoneal Sarcoma

BACKGROUND: The incidence of histopathologic organ invasion (HOI) in retroperitoneal sarcoma (RPS) is not well described. We reviewed our experience to investigate the rate and prognostic implications of HOI. STUDY DESIGN: Patients with primary RPS who underwent surgery at our institution were reviewed. Histopathologic organ invasion was defined as microscopic organ invasion confirmed by re-review of pathology slides by an expert sarcoma pathologist. Impact of HOI on the crude cumulative incidence of locoregional recurrence, distant recurrence, and overall survival rates was analyzed. RESULTS: Between 2002 and 2011, one hundred and eighteen patients underwent resection for primary RPS; 99 had at least 1 organ resected and, among those, HOI was present in 58% (57 of 99). Among the 77 patients with the 3 most common histologies, rates of HOI were 61% for dedifferentiated liposarcoma, 56% for leiomyosarcoma, and 40% for well-differentiated liposarcoma. In this subset, HOI was associated with no difference in 2-year crude cumulative incidence of locoregional recurrence (48% vs 47%; p = 0.55) or distant recurrence (46% vs 22%; p = 0.2). With a median follow-up of 33.6 months, HOI was an independent predictor of worse 5-year overall survival (34% vs 62%; p = 0.04; hazard ratio = 2.3; 95% CI 1.2 to 4.4; p = 0.02). CONCLUSIONS: The likelihood of organ invasion can be predicted by histologic subtype of primary RPS. To the best of our knowledge, this is the first study to demonstrate that HOI is associated with worse overall survival. These data can help guide the minimal extent of surgical resection required for RPS.