Multifocality in retroperitoneal sarcoma: A prognostic factor critical to surgical decision-making

Objective: To evaluate the significance of multifocality on overall survival (OS) in patients with retroperitoneal sarcoma (RPS) and establish a data-derived, prognostically and therapeutically useful definition of sarcomatosis. Summary Background Data: The incidence, clinical features, and prognostic significance of multifocality in RPS is unknown. No current standardized definition for sarcomatosis is available. Methods: We conducted a retrospective analysis of 393 patients with primary or recurrent nonmetastatic RPS treated at a comprehensive cancer center between 1996 and 2006. Baseline and treatment variables were compared in patients with unifocal and multifocal disease. A multivariate model was used to evaluate the association of multifocality and OS and identify additional prognostic factors in patients with multifocal disease. Results: The median follow-up time for all patients was 69 months; 79 patients (20%) presented with multifocal disease. The 5-year OS rate was less in the multifocal group compared with the unifocal group (31% vs. 60%, respectively; P < 0.0001). After multivariate analysis, multifocality remained an independent predictor of worse OS {hazard ratio (HR) 1.7 (95% confidence interval (CI), 1.2-2.5); P = 0.004}. Additionally, patients with more tumors had significantly worse prognosis (>7 tumors, HR 2.1 (95% CI, 1.1-3.9); P = 0.03), with a 5-year OS rate of 7%. Conclusions: Multifocal RPS is associated with worse OS in patients with either primary or recurrent RPS; Patients with >7 tumors had the worst prognosis. This criterion can be used to define sarcomatosis, thereby identifying patients whose survival will ultimately depend on effective systemic therapy.