Validation and adaptation of a nomogram for predicting the survival of patients with extremity soft tissue sarcoma using a three-grade system.

BACKGROUND: A nomogram for predicting long term tumor-specific death in patients with soft tissue sarcoma (STS) was developed at the Memorial Sloan-Kettering Cancer Center (MSKCC).

METHODS: To assess the performance of the MSKCC nomogram, 642 consecutive patients with extremity STS who underwent surgery over a 20-year span at a single referral center were analyzed. Nomogram predictions were based on tumor size, depth, site, patient age, histologic subtype, and grade. The latter, at variance with the system in use at the MSKCC, was classified as Grade 1-3 according to the French Federation of Cancer Centers Sarcoma Group (FNCLCC) system. The statistical approach used for nomogram performance assessment was that of "validation by calibration" proposed by Van Houwelingen.

RESULTS: Graphic comparison of observed and predicted sarcoma-specific survival curves showed that predictions by the nomogram were quite accurate, within 10% of actual survival for all prognostic strata. Statistical analysis showed that such predictions could be improved by employing approximately 25% shrinkage to achieve good calibration. The contribution of histologic grade was highly significant in both univariate analysis (P < 0.001) and multivariate analysis (P < 0.001), and a survival trend across the 3 grade categories was observed. Based on those findings, a nomogram that included the FNCLCC histologic grade classification was produced.

CONCLUSIONS: Results of the current study confirmed that the MSKCC nomogram is a valuable tool for individual prognostic assessment. A nomogram that included the FNCLCC histologic grade classification was proposed and was validated internally.