Postoperative nomogram for survival of patients with retroperitoneal sarcoma treated with curative intent

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Abstract
Background: Current American Joint Committee on Cancer retroperitoneal sarcoma (RPS) staging is not representative of patients with RPS specifically and has limited discriminative power. Our objective was to develop a RPS disease-specific nomogram capable of stratifying patients based on probability of overall survival (OS) after resection. Patients and methods: In all, 1118 RPS patients were evaluated at our institution (1996–2006). Patients with resectable, nonmetastatic disease were selected (n = 343) and baseline, treatment and outcome variables were retrieved. A nomogram was created and its performance was evaluated by calculating its discrimination (concordance index) and calibration and by subsequent internal validation. Results: Median follow-up and OS were 50 and 59 months, respectively. Independent predictors of OS were included in the nomogram: age (≥65), tumor size (≥15 cm), type of presentation (primary versus recurrent), multifocality, completeness of resection and histology. The concordance index was 0.73 [95% confidence interval (CI) 0.71–0.75] and the calibration was excellent, with all observed outcomes within the 95% CI of each predicted survival probability. Conclusions: A RPS-specific postoperative nomogram was developed. It improves RPS staging by allowing a more dynamic and robust disease-specific risk stratification. This prognostic tool can help in patient counseling and for selection of high-risk patients that may benefit from adjuvant therapies or inclusion into clinical trials.