Osteosarcoma mineralization changes on radiographs have moderate correlation to chemotherapy response using bone subtraction methodology

BACKGROUND: Survival following a diagnosis of osteosarcoma is correlated strongly with response to chemotherapy. Mineralization changes seen on radiographs have been hypothesized to correlate with chemotherapy response, however, this has never been analyzed using modern techniques. METHODS: Retrospective review of radiographs obtained before and after neoadjuvant chemotherapy was performed for 31 patients with high-grade, conventional osteosarcoma. Pre-chemotherapy (PreC) images and post-chemotherapy (PostC) images were co-registered. Tumor luminance measurements were normalized based on the non-tumor bone and then the relative change in tumor mineralization were measured. RESULTS: Mean luminance values for pre-chemotherapy non-tumor-affected bone and tumor were 0.63±0.12 and 0.65±0.12, respectively. Mean values for PostC non-tumor-affected bone were 0.59±0.14 and 0.64±0.10, respectively. Once normalized, osteosarcoma mineralization change showed a statistically significant moderate correlation—Pearson correlation coefficient (ρ) of 0.36 (P=0.038)—with the tumor necrosis value. CONCLUSIONS: Moderate, positive correlation was found between osteosarcoma mineralization change during chemotherapy and chemotherapy response. Further work is required to determine if these findings are prognostic by identifying best practice for image analysis and repeating this work with prospectively acquired digital radiographs using uniform technique and phantom normalization.