An examination of the efficacy of the 8 cm maximal tumor diameter cutoff for the subdivision of AJCC stage II osteosarcoma patients

Abstract

In the revised AJCC staging system a maximal tumor diameter of 8 cm was adopted as a cutoff for the subdivision of IIA and IIB osteosarcoma, but this cutoff was chosen based on limited information. We retrospectively reviewed 347 patients with stage II osteosarcoma that were treated at our institute. We plotted a receiver operating characteristic (ROC) curve of maximal tumor diameter for the prediction of subsequent metastasis, and calculated diagnostic indices according for different cutoffs. A maximal tumor diameter greater than 8 cm was found to predict subsequent metastasis with a sensitivity of 76.3%, a specificity of 49.5%, and a positive predictive value of 49.0% Almost half of stage IIB patients subsequently developed metastasis, whereas only a quarter of stage IIA patients did so. Tumor size had no prognostic relevance for proximal humeral tumors. The present study shows that an 8 cm maximal tumor diameter cutoff is useful for subdividing AJCC stage II osteosarcoma patients in terms of predicting of a subsequent metastatic event. Our results suggest that the IIA and IIB subdivision in the AJCC staging system provides a basis for risk-adapted therapy when used in combination with other prognostic factors.