Title: Threshold dose problems in radiation carcinogenesis: a review of non-tumour doses

Authors: Hiroshi Tanooka

Addresses: National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan

Abstract: Non-tumour-inducing doses exist in dose-response data on experimental animals and humans, although a linear non-threshold model has been adopted for estimating cancer risk of ionising radiation at a low dose region for radiation protection purposes. Here, data on non- tumour dose, Dnt, the maximum dose at which a statistically significant increase of tumours is not observed, were reviewed in the literature. Dnt values range from 0.1 to 3 Gy for a variety of tumours induced by acute whole-body irradiation at low LET. This becomes one order higher by fractionation of radiation dose and further by extending irradiation chronically. Non-tumour doses for irradiation of a part of the body are one order higher than those for whole-body irradiation, indicating a higher tolerance level in the partial-body irradiation. Tumour data with high LET radiation also show non-tumour dose and its decrease at a very low dose rate. The variation of Dnt is explained by the host tolerance, including inducible and non-inducible DNA repair, apoptotic elimination of unrepaired cells, and immunological suppression of tumour development.

Keywords: radiation; cancer; threshold dose; dose rate; review of cancer data; cancer risk; ionising radiation; low dose irradiation; tumor data.

DOI: 10.1504/IJLR.2004.005432

International Journal of Low Radiation, 2004 Vol.1 No.3, pp.329 - 333

Available online: 01 Oct 2004 *

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