Program Information
A Cortical Thickness Model to Predict Radiation-Induced Bone Fracture
M Munley*, C Okoukoni , E McTyre , M Farris , D Randolph , A Blackstock , J Willey , Wake Forest School of Medicine, Winston-Salem, NC
Presentations
SU-K-FS2-2 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: Four Seasons 2
Purpose: To apply a quantitative approach to measure cortical thinning as an early predictor of radiation-induced bone fracture.
Methods: We have developed a novel cortical thickness and radiation dose mapping approach that can identify site-specific and radiation dose- and volume-dependent thinning of cortical bone in patients receiving radiotherapy (RT). Cortical thickness is measured from pre- and post-treatment clinical CT scans using a validated density-based estimation model in order to create a bone cortical thinning map. Radiation dose received at bone surfaces during RT is then registered onto the map. We applied this cortical thickness and radiation dose-mapping approach as a means to measure rapid thinning i] of ribs after stereotactic body radiation therapy (SBRT) for primary or metastatic lung lesions (40 patients), and ii] in the hip and femoral neck after intensity modulated radiation therapy (IMRT) for anal cancer (22 patients).
Results: Substantial early thinning of the cortical bone was observed in a dose-dependent manner at 3-4 months follow-up in regions of ribs that absorb > 10 Gy during SBRT, and appeared localized at sites of fractures within the first year. Observed rib fractures were aligned with substantial (-15%) loss of cortical thickness. Additionally, thinning of the inferior-anterior and inferior-posterior portions of the femoral neck was observed in anal cancer patients receiving IMRT by < 4 months. V40 appears to be predictive of femoral cortical thinning.
Conclusion: Rapid thinning of the cortical bone is observed for regions receiving > 10 Gy. This observed bone cortical thinning in irradiated regions likely contributes to the occurrence of radiation-induced fracture in patients that received RT. This technique can also be used to define which skeletal sites are particularly radiation sensitive and therefore, delineate which areas we should limit dose in order to improve the quality of life for patients receiving RT.
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