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Mechanisms and Clinical Significance of Particle RBE

D Carlson1*, J Oden2*, F Kamp3*, H Paganetti4*, R Stewart5*, (1) University of Pennsylvania, Philadelphia, PA, (2) RaySearch Laboratories AB, Stockholm, SE, (3) University Hospital, LMU Munich, Munich, BV, DE, (4) Massachusetts General Hospital, Boston, MA, (5) University of Washington, Seattle, WA


(Tuesday, 7/14/2020) 3:30 PM - 4:30 PM [Eastern Time (GMT-4)]

Room: Track 5

Review mechanisms of action and biophysical insights related to proton and ion-therapy relative biological effectiveness (RBE) from laboratory experiments and clinical (planning) studies. The session will examine the mechanisms and effects of particle linear energy transfer (LET) from the perspective of in vitro and in vivo laboratory studies and the translation of data from laboratory studies into clinical practice, including uncertainties and opportunities for personalized plan optimization. The session will offer a mix presentations by junior and senior investigators with recent publications on the use of variable RBE models, as well as alternative LET- or track-end based, strategies for plan optimization and treatment evaluation.

Fundamental concepts and mechanisms of action will be reviewed and introduced at a level suitable for residents and practicing medical physicists that may or may not be familiar with RBE issues in proton and ion-therapy treatment planning. Other talks will focus on the clinical significance of variable RBE modeling for plan optimization, outcome assessment and the design of clinical trials. The session will conclude with a point-counterpoint debate on the proposition: Variable RBE models should be used for proton therapy plan optimization (RD Stewart for proposition; H. Paganetti against proposition).

Learning Objectives:

1. Understand that, for relevant molecular and cellular endpoints, particle RBE tends to increase with increasing LET up to a particle-specific peak and then either plateaus or decreases. The magnitude and trends in the observed RBE effects are qualitatively and quantitatively similar in vitro and in vivo.

2. Understand that the same molecular and cellular mechanisms give rise to spatial (and LET) dependent variations in proton and carbon ion RBE.

3. Recognize that variable RBE modeling is essential for treatment plan optimization and outcome assessment in carbon-ion therapy. Variable RBE modeling is controversial for the optimization and personalization of proton therapy plans.



RBE, Radiobiology


TH- Radiobiology(RBio)/Biology(Bio): RBio- general

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