Simple staging system for osteosarcoma performs equivalently to the AJCC and MSTS systems.

Both the American Joint Committee on Cancer (AJCC) and Musculoskeletal Tumor Society (MSTS) staging systems for skeletal sarcomas have major weaknesses. A revised staging system for osteosarcoma (the Vanderbilt system) was developed based on exploratory analyses of the relative prognostic impacts of histologic grade, tumor size, local tumor extension, and specific anatomic sites of metastasis using case records from the National Cancer Database (N = 4,285). AJCC, MSTS, and Vanderbilt staging schemes were then compared using a separate, population-based cancer registry (the Surveillance, Epidemiology, and End Results database; N = 2,246) as a validation dataset. Predictive accuracy for 5-year sarcoma-specific survival was evaluated by comparing areas under receiver-operating characteristic curves generated from logistic regression. Three different concordance indices and Bayesian information criteria were also calculated for model comparisons. The Vanderbilt staging system showed comparable predictive accuracy for 5-year disease-specific survival (65%) compared to the AJCC (67%) and MSTS (67%) staging systems. Most cross-comparisons of model concordance were not significantly different either. Bayesian information criterion was lowest for the MSTS staging system. Substaging osteosarcoma by current anatomical criteria is ineffectual. A simplified staging system based only on histologic grade and the presence of distant metastasis to any anatomic site performs similarly to the current AJCC and MSTS staging systems by multiple statistical criteria and is proposed for clinical and pathological staging of osteosarcomas of the non-pelvic appendicular and non-spinal axial skeleton. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2802-2808, 2018.