Ewing sarcoma (ES) and Osteosarcoma (OS) are the 2 most common malignant primary bone tumors. A patient's response to neoadjuvant chemotherapy has important implications in subsequent patient management and prognosis, as a favourable response to chemotherapy allows orthopedic oncologists to be more aggressive in pursuing limb-sparing surgery. An accurate and non-invasive pre-operative marker of response would be ideal for planning surgical margins and as a prognostic tool.

ES and OS have differing biological characterisitcs and respond differently to chemotherapy. We reviewed 18F-FDG PET imaging characteristics of ES and OS patients at baseline and following treatment to determine whether this biological variation is reflected in their imaging phenotype. A retrospective review of ES and OS patients treated with neoadjuvant chemotherapy and surgery was done, correlating PET results with histologic response to chemotherapy.

Change in the maximum standardized Uptake Value (SUVmax) between baseline and post-treatment scanning was not significantly associated with histologic response for either ES or OS. Metabolic tumor volume (MTV) and the percentage of injected 18F-FDG dose (%ID) in the primary tumor were found to be different for ES and OS response subgroups. A 50% reduction in MTV (MTV2:1 < 0.5) was found to be significantly associated with histologic response in OS. Using the same criteria for ES incorrectly predicted good responders. Increasing the cut-offs for ES to a 90% reduction in MTV (MTV 2:1 < 0.1) resulted in association with histologic response.

Response to neoadjuvant chemotherapy as reflected by changes in PET characteristics should be interpreted differently for ES and OS.

The aim was to identify when primary amputation was used as primary treatment and to describe outcomes in patients managed with modern chemotherapy. A detailed review of the electronic patient records was undertaken. Statistical analysis was performed with univariate analysis using Kaplan-Meier curves and Chi² testing, whilst multivariate analysis was performed using Cox regression analysis.

There were 354 osteosarcomas. 93 patients presented with metastases and 192 subsequently developed metastases at a mean of 46 months. Amputation was performed as the primary surgical treatment in 101 patients. Endoprosthetic reconstruction was used in 253 patients. Amputation was performed as a secondary procedure on 15 patients.

The 5 and 10 year survival data for all patients, including those with metastatic disease were 60% and 60% for amputation with good chemotherapy response (>89% necrosis), 65% and 63% for limb salvage and good response, 21% and 21% for amputation and poor response (⋋90% necrosis) and 51% and 30% for limb salvage with poor response.

Local recurrence occurred both with amputation (10.8%) or limb salvage (9%), with no significant differences between the two.

Univariate analysis demonstrated that the extent of response to chemotherapy induced necrosis significantly affected survival, whether the patient had an amputation or not.

Whether or not amputation or LSS was used in the surgical management of patients, local recurrence rates where similar between the two groups. Further assessment of chemotherapy-induced necrosis is a key factor in determining subsequent limb salvage or amputation management strategies.