Proton-Irradiation Effects in Primates

Zellmer, R.W.; Culver, James F.; Pickering, John E.

doi:10.2307/3583726

Cited by 2 publications

(1 citation statement)

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“…The majority of these experiments are in line with an RBE of about 1.1 relative to 60 Co. Specifically, reports considered mortality and hematological or cardiovascular changes in primates after whole body radiation (LD 50 ) (Kundel 1966, Dalrymple et al 1966a, 1966b, 1966c, Taketa et al 1967, Zellmer et al 1967, mice mortality after whole body irradiation (LD 50 ) (Tobias et al 1952, Bradley et al 1964, Baarli and Bonet-Maury 1965, Dalrymple et al 1966d, Ashikawa et al 1967, Jesseph et al 1968 or thorax irradiation (LD 50 ) (Stenson 1969b, Urano et al 1984, Gueulette et al 2000, as well as tumor induction and life shortening after whole body irradiation in mice (Clapp et al 1974). Some of these whole-body experiments were mainly done for space radiation research.…”

Section: Apoptosis and Cell Cycle Effectsmentioning

confidence: 94%

Relative biological effectiveness (RBE) values for proton beam therapy. Variations as a function of biological endpoint, dose, and linear energy transfer

2014

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Proton therapy treatments are based on a proton RBE (relative biological effectiveness) relative to high-energy photons of 1.1. The use of this generic, spatially invariant RBE within tumors and normal tissues disregards the evidence that proton RBE varies with linear energy transfer (LET), physiological and biological factors, and clinical endpoint. Based on the available experimental data from published literature, this review analyzes relationships of RBE with dose, biological endpoint and physical properties of proton beams. The review distinguishes between endpoints relevant for tumor control probability and those potentially relevant for normal tissue complication. Numerous endpoints and experiments on sub-cellular damage and repair effects are discussed. Despite the large amount of data, considerable uncertainties in proton RBE values remain. As an average RBE for cell survival in the center of a typical spread-out Bragg peak (SOBP), the data support a value of ~1.15 at 2 Gy/fraction. The proton RBE increases with increasing LETd and thus with depth in an SOBP from ~1.1 in the entrance region, to ~1.15 in the center, ~1.35 at the distal edge and ~1.7 in the distal fall-off (when averaged over all cell lines, which may not be clinically representative). For small modulation widths the values could be increased. Furthermore, there is a trend of an increase in RBE as (α/β)x decreases. In most cases the RBE also increases with decreasing dose, specifically for systems with low (α/β)x. Data on RBE for endpoints other than clonogenic cell survival are too diverse to allow general statements other than that the RBE is, on average, in line with a value of ~1.1. This review can serve as a source for defining input parameters for applying or refining biophysical models and to identify endpoints where additional radiobiological data are needed in order to reduce the uncertainties to clinically acceptable levels.

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