1279. The Value of Diffusion Weighted Imaging in Primary Osteogenic and Ewing Sarcomas for Monitoring Response to Treatment: Initial Experience
Authors * Denotes Presenting Author
  1. Karl Asmar; American University of Beirut
  2. Charbel Saade; American University of Beirut
  3. Rida Salman; Texas Children's hospital
  4. Nabil Khoury; American University of Beirut
  5. Lena Naffaa *; Nemours Childrens Hospital
To assess the value of using Apparent Diffusion Coefficient (ADC) mapping in Diffusion Weighted Imaging (DWI) when monitoring treatment response in pediatric Osteogenic and Ewing sarcomas and to correlate with level of necrosis on post-surgical excision pathology.

Materials and Methods:
This retrospective study includes 7 Osteosarcoma and 8 Ewing sarcoma patients. Pre-treatment and post-treatment focal MRIs were evaluated for ADC values, tumor volumes and variability of both measurements. We also compared the measurements between Ewing and Osteosarcoma groups, as well as between good (=/>90 % necrosis post-excision) and poor (< 90 % necrosis post-excision) responders.

All measurements except Maximum ADC (p = 0.20) showed a statistically significant difference when comparing them before and after treatment. When we segregated our population according to pathologic complete response, there was no difference in ADC measurements, volumetric measurements or either variability between good (8 Patients) and poor responders (7 Patients). When comparing the before-after changes in our measurement between the Ewing sarcoma and Osteosarcoma cases, there was no significant difference in the change between pre and post treatment (?) Mean or Maximum ADC, or in ?tumor-volume when measured on STIR or SPIR T1 post-contrast sequences. Only the ?Minimum-ADC showed a statistically significant difference (p<0.02) in this group.

ADC can potentially reflect cellular changes associated with chemotherapy use, reflecting a response to treatment. However, quantitative use of those parameters to dictate a change in management, treatment regimen or chemotherapy dose in order to target a good response (> / = 90 % necrosis post-excision) needs further investigation.