Program Information
Sensitivity of Relative Cell Survival to Oxygen Enhancement Ratio in Fractionated Radiotherapy with Hypoxia Targeted Dose Escalation
A Chvetsov*, J Rajendran , J Zeng , University of Washington, Seattle, WA
Presentations
SU-F-FS1-7 (Sunday, July 30, 2017) 2:05 PM - 3:00 PM Room: Four Seasons 1
Purpose: The uncertainties in the Oxygen Enhancement Ratio (OER) may have impact on the effectiveness of dose painting techniques based on dose escalation to hypoxic regions. The goal of this article is to compare the impact of Oxygen Enhancement Ratio (OER) on relative cell survival in conventional and hypofractionated radiotherapy with hypoxia-targeted dose escalation. The cell survival for non-uniform hypoxia-targeted dose distributions is computed relative to cell survival for a uniform dose distribution with equal integral tumor dose.
Methods: Our analysis is done using a parsimonious tumor response model that describes the major components of tumor response to radiotherapy such as radiosensitivity, cell proliferation and hypoxia using as few variables as possible. Two levels of oxygenated and hypoxic cells with the survival curves described by the Linear Quadratic (LQ) model are implemented in the model. The relative cell survival was computed for conventional and hypofractionated dose regimens in a model problem with radiobiological parameters for the non-small cell lung cancer.
Results: Our computational and analytical results show that relative cell survival is larger than 1.0 for the values of OER <1.4 in conventional fractionation; therefore, the uniform dose distribution is more efficient than the non-uniform hypoxia targeted dose distributions in cell killing under these conditions. For a hypofractionated dose regime (3x20Gy), the non-uniform hypoxia targeted dose distribution was more efficient in cell killing that a uniform dose distribution for the values of OER>1.05.
Conclusion: Our results indicate that the uniform dose distributions may be more efficient in cell killing not only for tumors with uniform radiosensitivity but also for the small OER values in conventional fractionation. For hypofractionated radiotherapy, the non-uniform hypoxia targeted dose distributions are more efficient in cell killing practically in the entire range of OER.
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