SU-E-T-245: Survival Fractions for Head-And-Neck Cancer Derived from Tumor-Volume Variation Curves Using a 2-Level Cell Population Model

Medical Physics
Alexei V Chvetsov, R Stewart

Abstract

Volumetric tumor response to radiotherapy is an integrated process which includes several radiobiological mechanisms, such as cell killing, cell proliferation, dead-cell removal and tumor reoxygenation. Our goal is to reconstruct the information about these underlying radiobiological processes and specifically the cell survival fractions by fitting a 2-level cell-population tumor-volume model to imaging-derived tumor-volume variation curves obtained during radiotherapy for head-and-neck cancer. Modeling tumor-volume during radiotherapy is a challenging problem because it is described by a sum of exponentials; therefore, the problem of accurately fitting a model to measured data is ill-posed. As an initial point of this research, we utilize a simplest 2-level cell-population tumor-volume model which separates the entire tumor-cell population into oxygenated viable cells and oxygenated lethally damaged cells. The 2-level cell population tumor model has the advantage of being conditionally well-posed. We integrated this parameterized radiobiological model with a least squares objective function and a simulated annealing optimization algorithm to characterize individual patients' time-dependent tumor-volume regression rates. The me...Continue Reading

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