Initial tumor size predicts histologic response and survival in localized osteosarcoma patients

Background: To evaluate the correlation between histologic response and size parameters, and to analyze the prognostic importance of size parameters on metastasis-free survival in localized osteosarcoma patients. Methods: We retrospectively reviewed 331 patients with stage II osteosarcoma treated with surgery and chemotherapy. The tumor size parameters were measured and calculated based on MR images. The mean metastasis-firee interval was 77.8 months (range, 3-205 months; median, 67 months). Results: Tumor size is best defined by relative tumor plane (RTP). Patients with a large tumor (RTP>27.5 cm(2)/m(2)) had a significant correlation with poor histologic response and distal femoral tumor location. The independent prognostic factors for metastasis-free survival were American Joint Committee on Cancer (AJCC) stage, RTP, proximal humerus location, chondroblastic subtype, and poor histologic response. Conclusion: The initial tumor size is closely related to histologic response and is an important prognostic factor in osteosarcoma. Tumor size is best represented by AJCC stage and RTP. These parameters may serve as a basis for risk-adapted therapy in combined stratification with histologic response.