Examination of the cutoff value of postchemotherapy increase in tumor volume as a predictor of subsequent oncologic events in stage IIB osteosarcoma.

Background: Tumor enlargement after chemotherapy is a predictor of a poor histological response, poor survival, and local recurrence. However, the cutoff point of tumor enlargement for predicting subsequent oncologic events has not been determined.
Methods: We retrospectively reviewed 567 patients who were treated at our institute for stage IIB osteosarcoma. We used receiver operating characteristic (ROC) curve analysis of tumor volume increase for the prediction of subsequent metastasis or local recurrence, and calculated diagnostic indices for different cutoff values.
Results: A tumor volume increase of >15% predicted subsequent metastasis or local recurrence with a sensitivity of 64.7%, a specificity of 81.5%, a positive predictive value of 71.6%, and a negative predictive value of 76.1%. Increases in tumor volumes based on this cutoff value were able to predict subsequent oncologic events in all clinical subgroups, except in cases of rare pathologic subtypes. However, for tumors in the proximal humerus, a cutoff value of 25% had optimal predictive value.
Conclusions: This study shows that a cutoff value of 15% for tumor volume increase is useful for predicting subsequent metastasis or local recurrence. Our results suggest that tumor enlargement after chemotherapy serves as an easily assessable clinical parameter for risk-adapted therapy.
(© 2013 Wiley Periodicals, Inc.)