November 14 Nov 14
12:00 PM - 01:00 PM
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Stanford University School of Medicine

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Medical Physics Seminar - David J Carlson

Advances in Biologically Guided Radiation Therapy for SBRT and Particle Therapy

12:00pm – 1:00pm Seminar & Discussion

Zoom Webinar

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Dr. David J Carlson, Professor, Vice Chair, & Director of Physics in the Department of Therapeutic Radiology at the Yale School of Medicine and Yale-New Haven Health

Dr. David J Carlson serves as the Professor, Vice Chair, & Director of Physics in the Department of Therapeutic Radiology at the Yale School of Medicine and Yale-New Haven Health. He completed his residency in Radiation Oncology Physics at Stanford University and received his PhD in Medical Physics from Purdue University. He is certified by the American Board of Radiology in Therapeutic Radiologic Physics. He currently serves as Executive Editor and Section Editor for Physics for the International Journal of Radiation Oncology, Biology, and Physics. He is a Fellow and past Member of the Board of Directors of the American Association of Physicists in Medicine (AAPM) and the Past Chair of the Science Education and Program Development committee of the American Society for Radiation Oncology (ASTRO). He was recently elected Fellow of the American Society for Radiation Oncology (FASTRO). The goals of Dr. Carlson’s research are to improve radiation therapy outcomes for cancer patients by developing accurate models of treatment response and to advance our understanding of the underlying biophysical mechanisms that govern radiation response.


In an era of increased treatment individualization and personalized medicine, accurate predictive models of dose-response are needed to guide treatment decisions and determine treatment effectiveness. Technological advances in radiation treatment delivery and image-guidance also continue to result in the delivery of more conformal dose distributions and improved normal tissue sparing. As a result, a trend has emerged to deliver higher doses per fraction in a fewer number of treatments. Although stereotactic body radiotherapy (SBRT) has become standard of care for certain tumor types, there remains a need to better understand the underlying mechanisms of treatment response to further optimize treatment planning and delivery. Does our conventional understanding of radiobiology apply to SBRT? Classical concepts in radiobiology and potential novel biological mechanisms will be critically examined. Recent studies suggest hypofractionation may result in decreased biological effectiveness for hypoxic tumors. Inter-tumor variation in hypoxia and reoxygenation may also impact treatment response. Serial imaging of human NSCLC tumors with 18F-FMISO PET indicates high single doses delivered as part of SBRT can induce an elevated and persistent state of hypoxia. Biophysical models can be used to evaluate the effectiveness of altered fractionations and facilitate the design and comparison of treatments. Local tumor control data for conventional radiotherapy and SBRT can be used to test models of treatment response and infer the role of secondary biological mechanisms. The available clinical data for early-stage NSCLC and brain metastases provide no clear evidence that unique mechanisms are required to explain the excellent clinical outcomes of SBRT. The linear-quadratic model with heterogeneity provides a reasonable approximation of clinical response at SBRT doses. Caution should still be taken with extreme hypofractionation due to tumor hypoxia. In particle therapy, the physical pattern of energy deposition and an enhanced RBE of particles compared to photons offer unique and not fully understood or exploited opportunities to improve treatment outcomes. Variations in RBE within a pristine or spread out Bragg peak and between particle types may be exploited to enhance cell death in target regions without increasing damage to normal tissues. The decreased radiosensitivity of hypoxic cells may be partially overcome through the use of more densely ionizing radiation. These and other differences between particles and photons may be used to generate biologically guided treatments. Recent work on improving simulations of radiation physics and RBE effects in proton, helium, and carbon ion therapy using the repair-misrepair-fixation (RMF) model will be presented. In addition to the physical advantages of protons and heavy ions, the future application of biologically optimized treatment plans has the potential to further improve patient outcomes.

A recording of the seminar will be available after the event.