Cancer risk at low doses of ionizing radiation: artificial neural networks inference from atomic bomb survivors

Sasaki, Masao S.; Tachibana, Akira; Takeda, Shunichi

doi:10.1093/jrr/rrt133

Cited by 52 publications

(50 citation statements)

References 144 publications

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“…Recent reanalysis has shown the data are more consistent with a threshold, or radiation hormesis, model than the linear nonthreshold (LNT) model. 4,5 In view of the above, we can conclude confidently that lowdose radiation is beneficial, not harmful, from both mechanistic and epidemiological considerations. …”

Section: Opening Statementmentioning

confidence: 90%

Point/Counterpoint: Low-dose radiation is beneficial, not harmful

Doss¹,

Little²,

Orton³

2014

Med. Phys.

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Section: Opening Statementmentioning

confidence: 90%

Point/Counterpoint: Low-dose radiation is beneficial, not harmful

Doss¹,

Little²,

Orton³

2014

Med. Phys.

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“…Vastly more accurate dosimetry estimates yielding more accurate dose-response relationships for leukemia were available in later years, starting with the tentative T65D system in 1965, the DS86 dosimetry system in 1986 and then the DS02 system in 2002. These later dose-response relationships obtained with more accurate data did not support the LNT model; rather, they exhibited nonlinearity at low doses (< 200 mGy) and a definite threshold (indeed, even exhibiting a negative excess relative risk, 13,14 suggesting a beneficial or cancer-preventative effect). Thus, as we have reported, 15 the cohort of A-bomb survivors, which is considered to be the single most important data source for estimating radiation effects in humans, no longer supports the LNT model, but rather supports a hormetic model exhibiting negative excess relative risk at low doses (< 200 mGy).…”

Section: Birth Of the Lnt Model Of Radiation Carcinogenesismentioning

confidence: 83%

The Birth of the Illegitimate Linear No-Threshold Model

Siegel¹,

Pennington²,

Sacks

et al. 2018

American Journal of Clinical Oncology

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This paper examines the birthing process of the linear no-threshold model with respect to genetic effects and carcinogenesis. This model was conceived >70 years ago but still remains a foundational element within much of the scientific thought regarding exposure to low-dose ionizing radiation. This model is used today to provide risk estimates for cancer resulting from any exposure to ionizing radiation down to zero dose, risk estimates that are only theoretical and, as yet, have never been conclusively demonstrated by empirical evidence. We are literally bathed every second of every day in low-dose radiation exposure due to natural background radiation, exposures that vary annually from a few mGy to 260 mGy, depending upon where one lives on the planet. Irrespective of the level of background exposure to a given population, no associated health effects have been documented to date anywhere in the world. In fact, people in the United States are living longer today than ever before, likely due to always improving levels of medical care, including even more radiation exposure from diagnostic medical radiation (eg, x-ray and computed tomography imaging examinations) which are well within the background dose range across the globe. Yet, the persistent use of the linear no-threshold model for risk assessment by regulators and advisory bodies continues to drive an unfounded fear of any low-dose radiation exposure, as well as excessive expenditures on putative but unneeded and wasteful safety measures.

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“…If a more generalized functional form was used, the conclusion would have been different, as the lower bounds of the 95% confidence intervals would have been below zero for low doses; more details are in [5]. The artificial neural networks method was reported to have circumvented the limitation of [22] and demonstrated the presence of a threshold of excess relative risk in humans exposed to ionizing radiation [27]. Along with the elevated risk of cancer mortality, an increased risk of non-neoplastic diseases including those of circulatory, respiratory (pneumonia, influenza etc.)…”

Section: Discussion Around Dose and Dose Rate Effectiveness Factor (Dmentioning

confidence: 99%

Biological Effectiveness of Ionizing Radiation: Acute vs. Protracted Exposures

2016

J Environ Stud

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This letter refers to the current discussion around re-evaluation of the dose and dose rate effectiveness factor (DDREF) equal to 2, presently recommended by the International Commission on Radiological Protection. The topics of the threshold, hormesis and DDREF are interrelated with the linear no-threshold theory (LNT). The LNT does not take into account that DNA damage and repair are permanent processes in dynamic equilibrium. Given the evolutionary prerequisite of best fitness, it would be reasonable to assume that living organisms have been adapted by the natural selection to the background levels of ionizing radiation. Accordingly, there must be an optimal exposure level, as it is for many environmental factors. Several studies cited in the literature in support of the LNT and lowering of the DDREF down to 1 are discussed here. In the author's opinion, the dose-effect relationships with non-neoplastic diseases found in certain exposed populations call in question dose-effect relationships with cancer. Self-selection and other biases in epidemiological studies are discussed. The dose-response relationships should be clarified in largescale experiments involving different animal species. In conclusion, the LNT and under-estimation of DDREF tend to exaggerate radiationrelated health risks at low radiation doses and dose rates. Arguments against Linear No-Threshold Theory (LNT)Radiation-related cancer risk estimates have been primarily based on the data from atomic bomb survivors. To adjust the risk estimates at acute exposures to low dose and continuous (low dose rate) exposures, a dose and dose rate effectiveness factor (DDREF) is used [1]. This letter refers to the discussion around re-evaluation of the DDREF value equal to 2, currently recommended by the International Commission on Radiological Protection (ICRP) [2]. The topics of the threshold, hormesis and DDREF are interrelated with the linear no-threshold theory (LNT). Hormesis and LNT are considered controversial by many scientists; discussion is in [3][4][5][6][7][8]. The LNT is corroborated by the following arguments: the more tracks go through a cell nucleus, the more DNA damage would result and the higher the risk of malignant transformation would be. "Decreasing the number of damaged cells by a factor of 10 would be expected to decrease the biological response by the same factor of 10" [9]. This concept does not take into account that DNA damage and repair are permanent processes in dynamic equilibrium. Given the evolutionary prerequisite of best fitness, it would be reasonable to assume that living organisms have been adapted by the natural selection to background levels of ionizing radiation [10]. Accordingly, there must be an optimal exposure level, as it is for many environmental factors: visible and ultraviolet light, different chemical elements and compounds [11], as well as the products from radiolysis of water [12]. Evolutionary adaptation to a changing environmental factor would lag behind its current value and correspond to some ...

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Cancer risk at low doses of ionizing radiation: artificial neural networks inference from atomic bomb survivors

Cited by 52 publications

References 144 publications

Point/Counterpoint: Low-dose radiation is beneficial, not harmful

Point/Counterpoint: Low-dose radiation is beneficial, not harmful

The Birth of the Illegitimate Linear No-Threshold Model

Biological Effectiveness of Ionizing Radiation: Acute vs. Protracted Exposures

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