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Program Information

Radiobiology for Hypofractionation: Basics for Clinical Physicists


E Yorke

P Medin

D Carlson




E Yorke1*, P Medin2*, D Carlson3*, (1) Memorial Sloan-Kettering Cancer Center, New York, NY, (2) UT Southwestern Medical Ctr at Dallas, Dallas, TX, (3) Yale Univ. School of Medicine, New Haven, CT

Presentations

MO-D-BRA|B-0 (Monday, March 20, 2017) 4:30 PM - 5:30 PM Room: Ballroom A|B


Radiobiology plays a critical role in the radiation therapy process, but it is still a dynamically developing field. As radiation treatments move steadily towards hypofractionation, made possible through advances in delivery and imaging technology, there remains a need to understand the underlying biological mechanisms to improve clinical outcomes. Our conceptual understanding and mathematical models of biological dose response are often based on in vitro or animal data leading to the question: how do the classical 5 R’s of radiobiology apply to the clinical paradigm of SRS and SBRT? Molecular imaging of inter-patient variation in radiosensitivy and treatment response may provide opportunities for treatment individualization for patients undergoing SBRT and SRS. In addition, how does the clinical physicist address re-irradiation following either conventional fractionation or SRS/SBRT while maintaining effectiveness in tumor response and normal tissue sparing? Data from both animal models and humans for the tolerance of the nervous system, which is of particular concern, will be presented. Finally, the AAPM’s Working Group on Biological Effects of Hypofractionated Radiotherapy is charged to generate reports based on critical review of the published data regarding tumor response and normal tissue tolerance of hypofractionation and to recommend standards for reporting outcomes, including endpoints, defining/contouring of target and normal structures and dose definitions.

Learning Objectives:
1. Understand how do the 5R’s apply to Hypofractionation and are conventional models valid at high doses per fractions?
2. Understand the current findings of the AAPM’s Working Group on Biological Effects of Hypofractionated Radiotherapy and related groups with additional focus on (a) normal tissue toxicity guidelines for SBRT lung – primarily the lung and esophagus (b) head and neck retreatment and (c) novel fractionation schedules.
3. Learn the current and cutting edge recommendations for normal tissue tolerances to the nervous system.



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