Dynamic treatment effect (DTE) curves reveal the mode of action for standard and experimental cancer therapies
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Kingshuk Roy Choudhury1, Stephen T. Keir2, Kathleen A. Ashcraft3, Mary-Keara Boss4 and Mark W. Dewhirst3
1 Department of Biostatistics and Bioinformatics, Duke University Medical Center, NC, USA
2 Preston Robert Tisch Brain Tumor Research Center, Duke University Medical Center, NC, USA
3 Department of Radiation Oncology, Duke University Medical Center, NC, USA
4 North Carolina State College of Veterinary Medicine, Department of Molecular Biomedical Sciences, NC, USA
Kingshuk Roy Choudhury, email:
Keywords: tumor growth delay, tumor growth modelling, inhibition rate, regrowth following radiotherapy, additive effects in combination therapy
Received: April 09, 2015 Accepted: April 09, 2015 Published: May 15, 2015
We present a method for estimating the empirical dynamic treatment effect (DTE) curves from tumor growth delay (TGD) studies. This improves on current common methods of TGD analysis, such as T/C ratio and doubling times, by providing a more detailed treatment effect and overcomes their lack of reproducibility. The methodology doesn’t presuppose any prior form for the treatment effect dynamics and is shown to give consistent estimates with missing data. The method is illustrated by application to real data from TGD studies involving three types of therapy. Firstly, we demonstrate that radiotherapy induces a sharp peak in inhibition in a FaDu model. The height, duration and timing of the peak increase linearly with radiation dose. Second, we demonstrate that a combination of temozolomide and an experimental therapy in a glioma PDX model yields an effect, similar to an additive version of the DTE curves for the mono-therapies, except that there is a 30 day delay in peak inhibition. In the third study, we consider the DTE of anti-angiogenic therapy in glioma. We show that resulting DTE curves are flat. We discuss how features of the DTE curves should be interpreted and potentially used to improve therapy.
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