Novel Scoring Criteria for Preoperative Prediction of Neoadjuvant Chemotherapy Response in Osteosarcoma

The extent of tumor necrosis after neoadjuvant chemotherapy is an important predictive factor of survival in osteosarcoma. However, the response to chemotherapy is not known until after the definitive resection and limits the utility of this information for operative planning. Our study questions include: 1) Are there clinical and radiographic factors following neoadjuvant chemotherapy, but prior to the tumor resection, that may aid in predicting response to treatment? 2) Can we combine these criteria into a predictive composite score that can identify good and poor responders to chemotherapy?

We identified consecutive patients diagnosed with osteosarcoma and managed with neoadjuvant chemotherapy prior to surgical resection. We assessed post-chemotherapy tumor ossification, tumor size and growth, and the presence of pain to devise a scoring criteria to predict the percent necrosis on the final histologic specimen. Bivariate analyses were done, and a receiver operating characteristic curve was constructed to determine predictive capacity.

Out of the 40 patients included in this study, 15 (38%) had a good response (≥ 90% necrosis) to treatment and ten patients (25%) had a poor response with ≤ 50% necrosis. Tumor size, growth and increase in ossification were significantly associated with a good response to treatment. For good responders, a composite score of 6 was seen to attain the highest sensitivity and specificity, 100% and 84%, respectively. Tumor size, no change in ossification, and post-chemotherapy pain were significantly associated with a poor response to treatment. For poor responders, a composite score of 7 was seen to have the highest sensitivity and specificity, 100% and 63%, respectively.

Compared to the use of one single factor, our combined scoring criteria demonstrated a far improved accuracy in identifying good responders to neoadjuvant chemotherapy, where a score of 6 or less is predictive of a good response. However, the specificity of this scoring criteria to predict poor responders was low, indicating that this criterion may not be the most accurate method to identify poor responders. The utility of this score has implications regarding pre-operative counseling of the patient and operative planning.Level of Evidence: III.