Session Information
2013 Spring Refresher Course
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Changing Fractionation Patterns (Hypofractionation)
Track : March 22, 2013
Program Code: 040
Date: Friday, March 22, 2013
Time: 1:00 PM to 2:45 PM  EST
Duration: 105 Minutes
Location: Grand Ballroom
Todd Pawlicki, PhD
Michael C. Joiner
For a sample set of anatomical structures, existing radiobiologic data and models predict improved clinical results from hypofractionation over standard fractionation for some tissues depending on alpha/beta ratios and other biological factors. Predicted results for specific patients may vary with individual anatomy, and largescale clinical conclusions can be drawn only after performing similar analysis on an appropriate population of patients. Hypofractionated treatment regimens will be compared with standard fractionation for a number of tumor sites using current radiobiologic models and
biologic parameters. The linear-quadratic model and generalized equivalent uniform dose formalism were used to calculate normalized equivalent uniform dose to compare tumor control probability and normal tissue complication probability and complication-free tumor control probability. The robustness of the results was tested for various tumor alpha/beta values and broad interval of biologic parameters such as surviving fraction after a dose of 2 Gy (SF2).On the treatment side, hypofractionated treatments involve precise patient repositioning and treatment delivery procedures. Treatments can last up to 2-3 conventionally fractionated treatment time slots. Precise patient setup is difficult to achieve especially with long treatment times because of tumor intra-fraction motion and patient involuntary movement during radiation delivery. Methods for effective treatment planning and radiation delivery of hypofractionated treatments will be presented. Technical challenges associated with the clinical implementation of hypofractionated treatments will be summarized and clinical solutions presented. These include immobilization to minimize patient movement, repositioning and monitoring of the patient during each treatment session to ensure accurate placement of beams, and accounting for intra-fraction organ motion.Planning of dose distributions to ensure tumor coverage will also be included as well as appropriate patient-specific QA methods.

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