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

Area of Science:

• Orthopaedic Oncology
• Skeletal Sarcoma Research
• Cancer Staging Systems

Background:

• Current American Joint Committee on Cancer (AJCC) and Musculoskeletal Tumor Society (MSTS) staging systems for skeletal sarcomas possess significant limitations.
• Existing systems may not accurately reflect the prognostic impact of key tumor characteristics for osteosarcoma.

Purpose of the Study:

• To develop and validate a revised staging system for osteosarcoma, termed the Vanderbilt system.
• To compare the predictive accuracy of the Vanderbilt system against established AJCC and MSTS staging schemes for osteosarcoma.

Main Methods:

• Exploratory analysis of prognostic factors (histologic grade, tumor size, local extension, metastasis site) using National Cancer Database (NCDB) data (N=4,285).
• Validation of the Vanderbilt, AJCC, and MSTS systems using a population-based Surveillance, Epidemiology, and End Results (SEER) registry dataset (N=2,246).
• Statistical comparison of predictive accuracy for 5-year sarcoma-specific survival using receiver-operating characteristic curves, concordance indices, and Bayesian information criteria.

Main Results:

• The Vanderbilt staging system demonstrated comparable predictive accuracy (65%) for 5-year disease-specific survival to the AJCC (67%) and MSTS (67%) systems.
• Most model concordance comparisons between the systems were not statistically significant.
• The MSTS staging system yielded the lowest Bayesian information criterion, suggesting a potentially more parsimonious model.

Conclusions:

• Current anatomical substaging criteria for osteosarcoma are considered ineffectual.
• A simplified staging system based solely on histologic grade and the presence of distant metastasis demonstrates comparable performance to current AJCC and MSTS systems.
• This simplified system is proposed for clinical and pathological staging of osteosarcomas affecting the non-pelvic appendicular and non-spinal axial skeleton.