title: Steepness of the radiation dose-response curve for dose-per-fraction escalation keeping the number of fractions fixed.
abstract: Clinically, there is growing interest in strategies for intensifying radiation therapy by escalating the dose per fraction. This paper considers the steepness of the dose-response curve in this case. The steepness of a radiation dose-response curve is most conveniently quantified by the normalized dose-response gradient, gamma. Under the assumption of a linear-quadratic dose-effect model, a simple analytical relationship is derived between the gamma-value for a dose-response curve generated by varying the total dose while keeping the number of fractions constant, i.e. escalating the dose per fraction, and the gamma-value for a dose-response curve generated by varying the total dose while keeping the dose per fraction constant. This formulation is compared with clinical dose-response data from the literature and shown to be in good agreement with the observations. Some implications of this formulation for non-uniform dose distributions delivered using 3D conformal radiotherapy or intensity modulated radiotherapy (IMRT) are briefly discussed.
authors.affiliation: Department of Human Oncology, University of Wisconsin Medical School, Madison, Wisconsin, USA. bentzen@humonc.wisc.edu
authors.forename: Søren M
authors.initials: SM
authors.lastname: Bentzen
mesh_terms: D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008433:Mathematics; D008954:Models, Biological