18F-FLT Positron Emission Tomography and Diffusion-Weighted Magnetic Resonance Imaging in Planning Surgery and Radiation Therapy and Measuring Response in Patients With Newly Diagnosed Ewing Sarcoma

The primary measure of the samples will be % of viable malignant cells remaining. To examine the correlation of 18F-FLT PET, 18F-FDG PET, and ADC signals in areas of concordance and discordance with standard MR imaging as it impacts differentiation of viable and necrotic tumor extent, sensitivity/specificity and positive/negative predictive values will be estimated. Findings will be summarized using point-estimates and corresponding 95% confidence intervals as appropriate. Differences in sensitivity and specificity will be evaluated using McNemar's test.

The primary measure of the samples will be % of viable malignant cells remaining. To examine the correlation of 18F-FLT PET, 18F-FDG PET, and ADC signals in areas of concordance and discordance with standard MR imaging as it impacts differentiation of viable and necrotic tumor extent, sensitivity/specificity and positive/negative predictive values will be estimated. Findings will be summarized using point-estimates and corresponding 95% confidence intervals as appropriate. Differences in sensitivity and specificity will be evaluated using McNemar's test.

The primary measure of the samples will be % of viable malignant cells remaining. To examine the correlation of 18F-FLT PET, 18F-FDG PET, and ADC signals in areas of concordance and discordance with standard MR imaging as it impacts differentiation of viable and necrotic tumor extent, sensitivity/specificity and positive/negative predictive values will be estimated. Findings will be summarized using point-estimates and corresponding 95% confidence intervals as appropriate. Differences in sensitivity and specificity will be evaluated using McNemar's test.

The primary measure of the samples will be % of viable malignant cells remaining. To examine the correlation of 18F-FLT PET, 18F-FDG PET, and ADC signals in areas of concordance and discordance with standard MR imaging as it impacts differentiation of viable and necrotic tumor extent, sensitivity/specificity and positive/negative predictive values will be estimated. Findings will be summarized using point-estimates and corresponding 95% confidence intervals as appropriate. Differences in sensitivity and specificity will be evaluated using McNemar's test.

The primary measure of the samples will be % of viable malignant cells remaining. To examine the correlation of 18F-FLT PET, 18F-FDG PET, and ADC signals in areas of concordance and discordance with standard MR imaging as it impacts differentiation of viable and necrotic tumor extent, sensitivity/specificity and positive/negative predictive values will be estimated. Findings will be summarized using point-estimates and corresponding 95% confidence intervals as appropriate. Differences in sensitivity and specificity will be evaluated using McNemar's test.

The prognostic ability of 18F-FLT PET and DW-MRI imaging will be evaluated by correlating changes in 18F-FLT uptake and ADC as treatment response both after chemotherapy (but prior to RT) and after RT with local control and survival outcomes, with the intent of establishing predictive thresholds. The results will be compared to standard prognostic factors such as change in tumor size and histopathology.

PET images and DW-MRI ADC maps co-registered and regions of concordance and discordance quantified for each modality as compared to pre-chemotherapy conventional MRI. The concordance correlation coefficient will be used to measure agreement between volumes generated at different times, with different modalities, and by different individuals. The measured variability associated with contrast-enhanced MRI will serve as the standard for comparison. The mean and standard deviation of volumes and their discordances will be calculated as a measure of the potential treatment impact of each modality.

Imaging thresholds to discriminate between > 90% and 100% necrotic tumor as established by pathology will be determined.

Treatment response as measured by the advanced imaging immediately following treatment will be compared to response as measured by conventional 18F-FDG PET follow-up imaging. In the case of local recurrence, patterns of local failure will be compared with imaging performed before and after local therapy.

For each patient the portion of the treated volume that is negative on PET or DW-MRI will be calculated to estimate the region of additional normal tissue that could be excluded from radiation treatment fields. Similarly, any volume that is positive on PET or DW-MRI, but outside of the post-chemotherapy treatment volume will be reported.

For each patient the portion of the treated volume that is negative on PET or DW-MRI will be calculated to estimate the region of additional normal tissue that could be excluded from radiation treatment fields. Similarly, any volume that is positive on PET or DW-MRI, but outside of the post-chemotherapy treatment volume will be reported.

To develop a standardized delineation technique for the 18F-FLT PET and DW-MRI images and reduce operator error and subjectivity, the variation of volumes defined with different segmentation techniques will be evaluated and compared against the biopsy determined imaging thresholds and expert Nuclear Medicine and MR Radiologist contours.