Should the radiological community continue the
present radiation dose-reduction campaign and efforts?
Mohan Doss, PhD, MCCPM Medical Physicist, Diagnostic Imaging,
Fox Chase Cancer Center, Philadelphia, PA, USA
E-mail: [email protected]
Revised and Updated version of the Presentation given at:
The 74th Annual Meeting of the Japan Radiological Society,
Yokohama, Japan, on April 17, 2015
Version 1.11
Copyright © 2015 by Mohan Doss.
This presentation in its entirety may be copied, shared, and distributed freely without any restriction. If using
individual slides or figures, please acknowledge this presentation as the source.
Disclaimer: Opinions expressed in this presentation are my own professional opinion, and do not necessarily
represent those of my employer.
1
☑ The author has no conflict of interest to
disclose with respect to this presentation.
2
The presentation was given as part of the Joint Symposium of
Japan Radiology Congress, 2015, Yokohama, Japan http://www.j-rc.org/jrc/2015/jsmp_prog_taikai.pdf
Joint Symposium 1
April 17 (Fri) 15:10～17:10 (Main Hall)
Patient Dose in Radiology: Manage the Invisible
Moderator: Aichi Medical Univ. Tsuneo Ishiguchi
NIRS Keiichi Akahane
1. We Can And We Must Reduce Radiation Exposure. Perspective of
The American College of Radiology American College of Radiology, USA Paul H. Ellenbogen
2. Radiation Protection (EUROSAFE IMAGING) University of Crete, Greece John Damilakis
3. Activities for the Management of Medical Radiation Exposure in Japan
Asahi General Hosp. Takayuki Igarashi
4. Should the Radiological Community Continue the Present Radiation
Dose-reduction Campaign and Efforts? Fox Chase Cancer Center, USA Mohan Doss
3
The answer depends on whether:
– Low-dose radiation is carcinogenic
– CT dose reduction efforts would result in
improved patient health.
Should the radiological community continue the present
radiation dose-reduction campaign and efforts?
4
The traditional answer is YES based on
the linear no-threshold (LNT) Model
5
Is Low-dose Radiation Carcinogenic?
Justification for the LNT Model
Radiation Free radicals DNA damage
Mutations Cancer
Linear relationships assumed.
Even a single ray of radiation DNA damage
Hence, No Threshold
Linear No-Threshold (LNT) Model
6
7
The Linear No-Threshold (LNT) Model
For higher doses,
Observe a linear relationship between
ERR and Radiation Dose
For low doses,
Large errors in determining ERR
Hence a Model is used for low doses.
In LNT model, ERR is extrapolated
from high doses to low doses
Does it make sense to extrapolate
the effect of radiation (or any other agent)
from high levels to low levels?
8
Do these types of extrapolations make sense?
To determine the effect of Extrapolate from the effect of
1 sleeping pill 50,100,200… sleeping pills
Drinking a cup of water
Drinking 1,2,3,..buckets of
water
Jumping from a step
Jumping from 5th, 10th, 15th,
… Floors of a building
9
No. Absolutely Not.
These types of extrapolations don’t make sense.
10
To determine the effect of Extrapolate from the effect of
1 sleeping pill 50,100,200… sleeping pills
Drinking a cup of water
Drinking 1,2,3,..buckets of
water
Jumping from a step
Jumping from 5th, 10th, 15th,
… Floors of a building
In a similar manner, for radiation,
To determine the effect of Extrapolate from
1-10 mSv radiation dose
1 Sv radiation dose
this type of extrapolation does not make sense:
LNT model is senseless
However, we have been using it for
more than fifty years.
When, and why did we start using it?
What is the origin of the LNT Model? 11
The first advisory body to adopt
the LNT Model
was the Genetics Panel of the
National Academy of Sciences (NAS)
Biological Effects of Atomic Radiation (BEAR) I
Committee in 1956.
(Calabrese, 2009)
12
Summary Report of BEAR I Genetics Committee
Published in Science, in 1956
Some of the statements in the summary report:
“The genetic harm is proportional to the total dose”
“there is no such figure other than zero” (for the amount of radiation
that is genetically harmless)
“our society should hold additional radiation exposure as low as it
possibly can”
The essence of the LNT model and ALARA principle are embodied in
these statements of the report.
The Report was also published in New York Times, received high
publicity, and resulted in public fear of low-dose radiation.
However, statements by the Committee Members in letters exchanged
between themselves next year expressed quite a different viewpoint 13
Statements in letters between Committee members in 1957
“I, myself, have a hard time keeping a straight face when there is talk
about genetic deaths and the tremendous dangers of irradiation. I
know that a number of very prominent geneticists, and people whose
opinions you value highly, agree with me.”
“Let us be honest with ourselves—we are both interested in genetics
research, and for the sake of it, we are willing to stretch a point
when necessary”, and
“Now, the business of genetic effects of atomic energy has produced
a public scare, and a consequent interest in and recognition of
importance of genetics. This is to the good, since it will make some
people read up on genetics who would not have done so otherwise,
and it may lead to the powers-that-be giving money for genetic
research which they would not give otherwise.”
See: (Calabrese, 2014) (Seltzer, 2007)
(Note: Keep a straight face = say it without laughing, or say it seriously.
Stretch a point = Exaggerate) 14
Excerpts from: Dobzhansky letter to Demerec (1957b) August 13 Letter, Milislav Demerec papers.
Reproduced with permission from American Philosophical Society Library. 15
BEAR I/II Committee Members:
•did not consider low levels of radiation to be dangerous
•were willing to exaggerate risk from low levels of radiation
to improve funding for genetics research
•were pleased that there was a public scare about the
genetics effects of radiation (after the publication of the
Genetics Panel Report), as it may lead to increased funding
for research
Such considerations among the Committee Members
indicate self-interest may have led the BEAR I
committee members to exaggerate the risk of low-dose
radiation by their adoption of the LNT model.
(Calabrese, 2014) 16
What are the consequences
of using the LNT Model?
17
18
The grey band covers the normal variation of baseline cancer rates (average
of male and female rates normalized to 100) during an extended period (1960-
1994) in which the cancer rates were relatively stable in Japan. See Table 9
on Page 80 of the report: Cancer Statistics in Japan, 2013 by Foundation for
Promotion of Cancer Research.
Cancer Mortality Rate vs. Radiation Dose
According to the LNT Model
19
Dose reduction efforts
10 mSv down to 1 mSv (e.g.)
- cancer rate stays within grey area
- 0.15% reduction of cancer
mortality rate while the range of
natural variation is ±2%
- no health benefit.
- a total waste of resources
Of course, wasted resource for the
public are BIG $$$$$ for the LNT
model proponents and the resulting
enterprises.
Impact of Dose Reduction Efforts in Diagnostic Imaging
on Cancer Mortality Rate, according to the LNT Model
Financial motivation that apparently initiated the LNT model appears to be the reason
for its persistence and expansion into radiology, since there is no health benefit to the
patients from its use but huge financial benefit to the resulting enterprises including
research.
Is the LNT Model valid?
Let us examine the evidence.
20
Cancer risk in populations exposed to
low-dose radiation
21
50 mSv 100 mSv
40 mSv
500 mSv
All the data show reduction of
cancers following low-dose
radiation exposures
23
Additional Data on Cancer risk in Populations
Exposed to Low-dose Radiation
All the data show no increase in cancers or reduction of cancer for low doses.
How can we explain the observed reduced
cancers or no increase in cancers following low-
dose radiation exposures in so many instances?
Didn’t the LNT model arguments
(Radiation DNA damage Mutations Cancer)
show the smallest radiation dose should
increase cancers?
Explanation:
There are major defects in
the LNT Model arguments.
24
Major Defects of the LNT Model arguments
25
DNA damage occurs even in the absence of low-dose radiation due to
endogenous causes. Low-dose radiation results in increased defenses known
as adaptive protection (Feinendegen, 2013) consisting of antioxidants, DNA
repair enzymes, apoptosis, etc. which would reduce the endogenous damage
that would have occurred in the absence of the low-dose radiation. Thus, there
would be less overall DNA damage following low-dose radiation exposure, as
seen in the above data.
DNA damage does not increase linearly with dose at low doses.
LNT Model argument assumes increased mutations mean increased cancers.
However mutations do not imply cancer.
Almost everyone has cancerous mutations, see (Greaves, 2014),
but everyone does not have cancer. 26
Percentage of patients with cancerous mutations is unchanged
But Cancer mortality rate increases drastically with age.
Major Defects of the LNT Model arguments
The LNT model completely ignores the immune system which plays a
major role in preventing covert cancers from becoming clinical cancers.
Low-dose radiation boosts the immune system response, and so would
reduce cancers. 27
Major Defects of the LNT Model arguments
Suppression of the immune system increases cancer risk by a factor of ~3,
demonstrating how important immune system is for keeping covert cancers in
check. Immune system response declines rapidly with age, qualitatively
explaining the age-related increase in cancers. Low-dose radiation boosts the
immune system.
Are Low-dose Radiation exposures
of concern for children?
Data generally shown to raise the concerns However, excess cancers
are observed for high-dose
radiation exposures only in
atomic bomb survivors.
Only by LNT model
extrapolation, these
graphs are extended to
low-doses.
But since there is no
evidence/justification for
the LNT model, extension
of the graph to low doses
is not valid. 28
Other arguments used to raise concerns:
Children
- have higher proportion of dividing cells,
- more susceptible to mutations due to radiation.
This argument ignores adaptive protection.
Low-dose radiation adaptive protection
- reduces overall mutations
- enhances the immune system
- would reduce cancers
NO CONCERNS REGARDING LOW-DOSE RADIATION
EXPOSURES TO CHILDREN, e.g. from CT scans 29
Are children at risk from low-dose radiation?
The most important data for determining
the health effects of radiation are
the atomic bomb survivor data.
30
Importance of the Atomic Bomb Survivor data
31
BEIR VII Report, 2006
Page 141
Hall and Brenner, Cancer risks from diagnostic radiology, BJR, 81, 2008, p362-378
Page 323
Linearity in the Atomic Bomb Survivor Data
(after the latest update in 2012)
Atomic bomb survivor data no longer have a linear dose-response.
Excess relative risks for low doses near zero would be lower due to adaptive
protection, as seen in data in earlier slides. Since these ERRs extrapolated to zero
dose were used as baseline cancer rates in the fitting process for determining the
ERRs by Ozasa et al, the baseline cancer rates would have a negative bias.
Ozasa et al. state:
(Ozasa et al, 2012) Page 234
Page 238
32
33
The shape of dose-response curve, with the correction for the negative bias in
the baseline cancer rate, is consistent with the concept of radiation hormesis.
Threshold Dose in Atomic Bomb Survivor Data
Dose-Threshold Analysis (Ozasa, 2012)
- used linear dose-response model shape
(this shape did not cover the full range of
observed ERR values, i.e. negative values)
- concluded zero dose is the best estimate of threshold dose
Analysis using a more general functional form
- Comments in Radiation Research by
(Doss, Egleston, Litwin, 2012)
- conclusion: finite threshold dose is possible.
Ozasa et al. had no response/rebuttal to these Comments.
34
Opening Statement of Counterpoint by Dr. Little:
Did not use atomic bomb survivor data (the most important
data according to LNT model supporters) to claim cancer risk
from low-dose radiation
In earlier debates,
The atomic bomb survivor data played a major role.
Conclusion: The atomic bomb survivor data no longer
provide evidence for the LNT model, even according to the
LNT model supporters.
Recent debate in Medical Physics, 41, 070601 (2014)
Low-dose Radiation is Beneficial, Not Harmful,
Authors: Doss, Little, Orton.
35
Major Consequences from the Change in the
Nature of Atomic Bomb Survivor Data in 2012
In the past, Atomic Bomb Survivor Data have been utilized in
most publications, reports, research funding applications, etc.
as the key data to claim support for carcinogenicity of low-
dose radiation or for the LNT model.
Such publications and reports (and any consequential
publications that claim low-dose radiation cancer risk) should
not be used any longer since the atomic bomb survivor data
no longer support the LNT Model. Such publications will be
tagged with the label:
Also, any funding applications for research dated 2013 and
later that justify low-dose radiation cancer risk based on the
LNT model or atomic bomb survivor data should be rejected
retroactively since they should never have been approved.
36
Are there any evidences to support the
LNT model or the concept that low-dose
radiation causes cancer?
Many publications have made such claims, they get
huge publicity, are cited by many other publications, but
are later found to be faulty, with their conclusions being
reversed.
The damage – misleading the professionals and the
public about the carcinogenicity of low-dose radiation -
has already been done, and continues for a long time.
37
What to do with such faulty publications?
The faulty publications should be tagged
and they should not be used. Any
publications that utilize the faulty
publications to justify low-dose radiation
concerns should also be tagged
and should not be used.
Two such recent publications will be
discussed now.
38
Studies Claiming Increased Cancers Following
Childhood CT Scans
(Pearce, et al, 2012) UK Study:
Claimed increased leukemias and brain cancers
770 citations in Google Scholar
(Mathews, 2013) Australian Study:
Claimed increased cancers of many types
309 citations in Google Scholar
Created a lot of buzz in popular media, and concerns among the
public regarding children’s CT scans.
Study was criticized and its conclusions questioned by many, with
no rebuttal from the authors.
See:
(Cohen, 2013), (Walsh, 2013), (Boice, 2013), (Walsh, 2014), (Socol, 2015)
39
(Pearce, et al, 2012) UK Study:
Brain Cancers:
• ERR/Gy for glioma increased with
age at exam – this is reverse of
prior studies. The risk is expected
to decrease for higher ages when
brain development nears
completion (UNSCEAR 2013)
• ERR/Gy =23 much higher than
0.88, observed in A-Bomb
survivors <10 y
Leukemias and MDS:
• ERR/Gy Leukemia and
Myelodysplastic Disease (MDS) –
36, much higher than 6.5 in A-
Bomb Survivors <20y
(Mathews, 2013) Australian Study:
All cancers:
Risk estimate for All cancers (excluding brain
cancers) was 27 vs 3 for A-bomb survivors
Latency period:
Study of cancers one year after CT scans
increased the likelihood of reverse causation
Implausible tumors associated with CTs:
Excesses seen for melanoma and Hodgkin’s
lymphoma, not known to be associated with
radiation, and not for breast cancer, a
radiosensitive site
Inconsistent Age at exposure effect:
Excess leukemias observed for later age
exposure but not for early age, contrary to
other earlier studies.
Both studies were subject to reverse causation because of study design. Considering
the large inconsistencies with previous studies, the conclusions of these studies are in
doubt, and so these studies do not provide evidence for causal link between CT scans
and cancers (Boice, 2013). The conclusions of these publications are not credible.
Discussion of Recent Publications Claiming Increased Cancers
following Childhood CT scans as described in (Boice, 2013)
40
In the following slides, several publications
that raise low-dose radiation concerns are
examined to determine if they have referred
to older atomic bomb survivor data or faulty
publications to claim cancer risk from low-
dose radiation. If they have, then they
would be tagged .
41
42
Author(s)/Journal/
Title
Arguments or articles cited to
justify low-dose radiation cancer
concerns
Reason Why Arguments or Articles Cited
are Not a cause for concern Disposition of
Publication
BEIR VII Report
(NRC, 2006) Health risks from
exposure to low
levels of ionizing radiation
Atomic Bomb Survivor Data
(from 2006 and earlier)
Superseded by newer data (Ozasa et al.,
2012) which no longer support the LNT
model; see (Doss, 2012, Doss, 2013);
BEIR VII
radiation
cancer risk
model no
longer valid
(Cardis et al., 2005) Study Conclusion no longer valid due to
faults identified in Canadian Data. See
(CNSC, 2011, Zablotska et al., 2014)
(Brenner and Hall,
2007)/NEJM
Computed
tomography--an
increasing source of
radiation exposure
Concerns raised about DNA
double strand breaks due to
radiation exposure
Completely ignores adaptive protection in
the body which would reduce the naturally
occurring damage in the subsequent
period, resulting in less overall DNA
damage. See e.g. (Koana, 2010, Osipov,
2013) Conclusion of
Publication no
longer valid Atomic Bomb Survivor Data
(Preston et al., 2007)
Superseded by newer data (Ozasa et al.,
2012) which no longer support the LNT
model; see (Doss, 2012, Doss, 2013);
15 Country Study of Radiation
Workers (Cardis et al., 2005)
Study Conclusion no longer valid due to
faults identified in Canadian Data. See
(CNSC, 2011, Zablotska et al., 2014)
Author(s)/Journal/Title Arguments or articles cited to
justify low-dose radiation cancer
concerns
Reason Why Arguments or
Articles Cited are Not a cause for
concern
Disposition of
Publication
(Berrington de
González, 2009) /Arch.
Int. Med./ Projected cancer risks from
computed tomographic scans
BEIR VII report radiation cancer
risk model BEIR VII Report conclusions no
longer valid
Conclusion of
Publication no longer
valid
(Smith-Bindman,
2009) / Arch. Int. Med/ Radiation dose associated
with common computed tomography examinations
BEIR VII Report radiation cancer
risk estimates BEIR VII Report conclusions no
longer valid
Conclusion of
Publication no longer
valid
(FDA, 2010) White Paper - Initiative
to Reduce Unnecessary
Radiation Exposure from
Medical Imaging
(Brenner and Hall, 2007,
Berrington de Gonzalez et al.,
2009, Smith-Bindman et al.,
2009)
Cited publications' conclusions no
longer valid.
Conclusion of
Publication no longer
valid
(Pearce, 2012) /
Lancet/ Radiation exposure from
CT scans in childhood
and subsequent risk of
leukaemia and brain tumours
ERR/Gy for glioma increased
with age at exam; This is reverse of prior studies
Because of large
inconsistencies with
previous data, and
because the study
design that allowed
reverse causation,
Conclusion of
Publication not
credible.
see (Boice, 2013)
ERR/Gy =23 ; ERR/Gy much higher than 0.88,
observed in A-Bomb survivors less
than 10 y old.
ERR/Gy Leukemia and MDS ~
36 Much higher than 6.5 in
A-Bomb Survivors <20y
Reason for CT scans not
specified. Likelihood of Reverse Causation 43
Author(s)/Journal/
Title
Arguments or articles cited to
justify low-dose radiation cancer
concerns
Reason Why Arguments or
Articles Cited are Not a cause for
concern
Disposition of
Publication
(Mathews, 2013) / BMJ/ Cancer risk in 680,000
people exposed to
computed tomography
scans in childhood or adolescence
Risk estimate for All cancers
(excluding brain cancers) was 27 Was 3 for A-bomb survivors
Because of so
many
inconsistencies
with previous data,
and because of the
deficiencies in the
study design that
allow reverse
causation,
Conclusion of
Publication not
credible.
see (Boice, 2013)
Excesses seen for melanoma and
Hodgkin’s lymphoma, and not for
breast cancer
Melanoma and Hodgkin’s
lymphoma are not known to be
associated with radiation. Breast
cancer known to be associated
with radiation.
Excess leukemias observed for
later age exposure but not for
early age
This is contrary to other earlier
studies.
Cancers just one year after CT
scans were included in the study Increased the likelihood of
reverse causation
THE FOLLOWING PUBLICATIONS USED REFERENCES WHOSE CONCLUSIONS WERE ALREADY NEGATED BECAUSE OF UPDATED DATA OR IDENTIFICATION OF FAULTS.
(Brenner, 2014) / BJR/ What we know and what we
don't know about cancer
risks associated with
radiation doses from radiological imaging.
(Cardis et al., 2005,
Preston et al., 2007,
Pearce et al., 2012,
Mathews et al., 2013)
(Preston, 2007) was superseded
by newer data (Ozasa et al.,
2012) which no longer support
the LNT model; see (Doss, 2012,
Doss, 2013); Conclusions of
other publications no longer valid
or not credible.
Conclusion of
Publication invalid
44
Author(s)/Journal/
Title
Arguments or articles cited to
justify low-dose radiation cancer
concerns
Reason Why Arguments or Articles
Cited are Not a cause for concern Disposition of
Publication
(Redberg and Smith-
Bindman, 2014) /
New York Times/ We are Giving
Ourselves Cancer
(Berrington de Gonzalez et al.,
2009, Pearce et al., 2012,
Mathews et al., 2013)
Conclusions of Publications are not
credible or are no longer valid.
Conclusion of
Publication invalid
(Smith-Bindman and
Boone, 2014)/ JACR/ Introduction to the
special issue:
radiation dose
optimization
(Preston et al., 2007, Pearce et
al., 2012, Mathews et al., 2013),
BEIR VII Report
(Preston et al., 2007) was
superseded by newer data (Ozasa
et al., 2012) which no longer
support the LNT model. see (Doss,
2012, Doss, 2013); Conclusions of
other publications are not credible
or are no longer valid.
Conclusion and
recommendations of
Publication invalid
(EPA, 2014)/ FEDERAL GUIDANCE
REPORT NO. 14
Berrington de González et al.
2009; Brenner 2007; Smith-
Bindman et al. 2009; Pearce et
al. 2012; Mathews et al. 2013.
Conclusion of Publications no
longer valid or not credible.
Recommendations of
Publication not
justified.
(Consumer Reports,
2015)/ The Surprising
Dangers of CT Scans and X-rays
(Berrington de Gonzalez et al.,
2009, Pearce et al., 2012,
Mathews et al., 2013)
Conclusions of Publications are not
credible or are no longer valid.
Conclusion and
recommendations of
Publication invalid.
45
References:
Berrington de Gonzalez, A., et al. 2009. Projected cancer risks from computed tomographic scans performed in the
United States in 2007. Arch Intern Med, 169, 2071-7. http://www.ncbi.nlm.nih.gov/pubmed/20008689
Boice, J. D. 2013. Paediatric CT and Recent Epidemiological Studies.
http://www.icrp.org/docs/John%20Boice%20Paediatric%20CT%20and%20Recent%20Epidemiological%20Studies.pdf
Brenner, D. J. 2014. What we know and what we don't know about cancer risks associated with radiation doses from
radiological imaging. Br J Radiol, 87, 20130629. http://www.ncbi.nlm.nih.gov/pubmed/24198200
Brenner, D. J. & Hall, E. J. 2007. Computed tomography--an increasing source of radiation exposure. N Engl J Med,
357, 2277-84. http://www.ncbi.nlm.nih.gov/pubmed/18046031
Cardis, E., et al. 2005. Risk of cancer after low doses of ionising radiation: retrospective cohort study in 15 countries.
BMJ, 331, 77. http://www.ncbi.nlm.nih.gov/pubmed/15987704
CNSC. 2011. INFO-0811. Verifying Canadian Nuclear Energy Worker Radiation Risk: A Reanalysis of Cancer Mortality
in Canadian Nuclear Energy Workers (1957-1994) Summary Report, Canadian Nuclear Safety Commission. [Online].
http://nuclearsafety.gc.ca/pubs_catalogue/uploads/INFO0811_e.pdf Published June 2011.
Consumer_Reports. 2015. The Surprising Dangers of CT Scans and X-rays. Consumer Reports, March, 2015.
http://www.consumerreports.org/cro/magazine/2015/01/the-surprising-dangers-of-ct-sans-and-x-rays/index.htm
Doss, M. 2012. Evidence supporting radiation hormesis in atomic bomb survivor cancer mortality data. Dose
Response, 10, 584-92. http://www.ncbi.nlm.nih.gov/pubmed/23304106
Doss, M. 2013. Linear No-Threshold Model vs. Radiation Hormesis. Dose Response, 11, 480-497.
http://www.ncbi.nlm.nih.gov/pubmed/24298226
EPA. 2014. FEDERAL GUIDANCE REPORT NO. 14 - Radiation Protection Guidance for Diagnostic and
Interventional X-Ray Procedures . http://www.epa.gov/radiation/federal/fgr-14.html
FDA. 2010. White Paper - Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging, 2010, Center
for Devices and Radiological Health, FDA.
http://www.fda.gov/Radiation-EmittingProducts/RadiationSafety/RadiationDoseReduction/ucm199994.htm
Koana, T. & Tsujimura, H. 2010. A U-shaped dose-response relationship between x radiation and sex-linked
recessive lethal mutation in male germ cells of Drosophila. Radiat Res, 174, 46-51.
http://www.ncbi.nlm.nih.gov/pubmed/20681798
46
References (continued):
Mathews, J. D., et al. 2013. Cancer risk in 680,000 people exposed to computed tomography scans in
childhood or adolescence: data linkage study of 11 million Australians. BMJ, 346, f2360.
http://www.ncbi.nlm.nih.gov/pubmed/23694687
NRC 2006. Health risks from exposure to low levels of ionizing radiation : BEIR VII Phase 2, National
Research Council (U.S.). Committee to Assess Health Risks from Exposure to Low Level of Ionizing
Radiation., Washington, D.C., National Academies Press. http://www.nap.edu/catalog.php?record_id=11340
Osipov, A. N., et al. 2013. In vivo gamma-irradiation low dose threshold for suppression of DNA double strand
breaks below the spontaneous level in mouse blood and spleen cells. Mutat Res, 756, 141-5.
http://www.ncbi.nlm.nih.gov/pubmed/23664857
Ozasa, K., et al. 2012. Studies of the mortality of atomic bomb survivors, Report 14, 1950-2003: an overview
of cancer and noncancer diseases. Radiat Res, 177, 229-43. http://www.ncbi.nlm.nih.gov/pubmed/22171960
Pearce, M. S., et al. 2012. Radiation exposure from CT scans in childhood and subsequent risk of leukaemia
and brain tumours: a retrospective cohort study. Lancet, 380, 499-505.
http://www.ncbi.nlm.nih.gov/pubmed/22681860
Preston, D. L., et al. 2007. Solid cancer incidence in atomic bomb survivors: 1958-1998. Radiation Research,
168, 1-64. http://www.ncbi.nlm.nih.gov/pubmed/17722996
Redberg, R. F. & Smith-Bindman, R. 2014. We are Giving Ourselves Cancer. New York Times, Jan 30, 2014.
http://www.nytimes.com/2014/01/31/opinion/we-are-giving-ourselves-cancer.html?_r=0
Smith-Bindman, R. & Boone, J. M. 2014. Introduction to the special issue: radiation dose optimization--
improving the safety of CT. J Am Coll Radiol, 11, 229-30. http://www.ncbi.nlm.nih.gov/pubmed/24589393
Smith-Bindman, R., et al. 2009. Radiation dose associated with common computed tomography
examinations and the associated lifetime attributable risk of cancer. Arch Intern Med, 169, 2078-86.
http://www.ncbi.nlm.nih.gov/pubmed/20008690
Zablotska, L. B., et al. 2014. A reanalysis of cancer mortality in Canadian nuclear workers (1956-1994) based
on revised exposure and cohort data. Br J Cancer, 110, 214-23.
http://www.ncbi.nlm.nih.gov/pubmed/24231946
47
Manuscripts submitted after 2012 with the
claim of low-dose radiation cancer risk
based on the LNT model or using older
atomic bomb survivor data should not have
been approved for publication, since the
(Ozasa, 2012) update to the atomic bomb
survivor data do not support the LNT model.
48
As seen in the Table in the previous slides, a
large number of influential publications continue
to use the old atomic bomb survivor data (or
publications based on such data) to justify the
LNT model or low-dose radiation cancer concerns
when the updated atomic bomb survivor data do
not support the LNT model. Such publications
generate a tremendous amount of economic
activity (research, dose reduction and monitoring
efforts, etc.) which do not benefit the public but
financially benefit the resulting enterprises. Public
funding of such work is not justifiable, and should
be terminated. 49
Recent Research Funding Should be Reviewed
Any research projects publicly funded since 2013
should be reviewed to determine if they were
justified by low-dose radiation concerns based on
the LNT model. If so, the research funding for the
projects should be terminated, since they should
not have been approved in the first place, because
the newer atomic bomb survivor data, which are
recognized to be the most important data and gold
standard data, do not support the LNT model any
longer.
50
Update to BEIR VII Report being considered by NAS
At the recent scoping meeting for BEIR VIII Report
Speakers referred to studies that are not credible or whose
conclusions have been negated due to identification of faults
– Cancers following pediatric CT scans (Pearce, 2012; Mathews, 2013)
– 15-Country Study of Radiation Workers (Cardis, 2005)
to claim increased low-dose radiation cancer risk
But ignored evidences:
– Deviation from linearity of atomic bomb survivor data (Doss 2012,2013)
– Nuclear Shipyard Worker Study (Sponsler and Cameron, 2005)
– Study of second cancers in radiation therapy patients (Tubiana, 2011)
showing decreased cancer risk from low-dose radiation
51
BEIR VIII should not be funded in view of such bias.
In summary, dose reduction
campaign and efforts in diagnostic
imaging do not benefit patients by
reducing cancer risk but financially
benefit the resulting enterprises by
increasing economic activity,
research, etc.
52
Now let us discuss the impact of the fear
and concerns that have been raised about
CT scans by articles incorrectly claiming
they cause cancers, and the efforts to
reduce the radiation dose from CT scans.
53
Caution about harm caused to patients by
cancer concerns from diagnostic imaging
(Brody, 2014) in Thorax
54
This article describes many ways in which
actions taken due to the current radiation dose
concerns about CT scans can harm patients.
Consequences of Misinforming Patients/Parents
About Cancer Risk from CT scans
55
When patients or parents are misinformed that there is
increased risk from CT scans, some fraction of them
would refuse the CT scans. What they gain by refusing
the scan is nothing, even if LNT model projection is true,
since the change in cancer risk is within the range of
normal variation from year to year (see figure on right),
but they have lost the diagnostic information that could
potentially be lifesaving.
Stress in patients/parents following CT scans
Example of text in emails from concerned parent:
• At the moment I am googling like mad as concerned
about my 1 year old daughter having CT scan after
falling and fracturing her skull. Thankfully all is well.
• It is tantamount to mental cruelty what is being written
and reported about radiation effects from CT scans, I
saw many other mothers had made entries on web
sites regarding the CT scan their child had and their
concerns for future cancers.
56
See comment on next page.
Stress in patients/parents following CT scans
Example of text in email from concerned patient
I am familiar with the controversy and debate concerning
<100 mSv exposures, hormesis, and the “consensus” on the
LNT. Still, I am having a difficult time moving on with my life
despite it all. I see constant reminders of the risks of CT
everywhere in the media, and those stories often warn against
the risks of a SINGLE scan. It is absolutely terrifying to think that
I have had 5 scans, and that consequently a latent cancer is
waiting to manifest.
This matter has caused me such paralyzing anxiety….
57
We should not be causing this type of concerns in
patients/parents by misinforming them about the risks of
diagnostic imaging. The increased risks claimed are
phantom risks because they are based on the invalid LNT
model, and even if the LNT model is believed to be valid,
the increased risk is within the normal variation in cancer
rates from year to year (see figure on right).
Physicians influenced in imaging decisions
by radiation dose concerns
58
When physicians are misinformed that there is increased
cancer risk from CT scans, some fraction of them would
refuse to order the appropriate CT scans. What they gain by
refusing to order the CT scans is nothing, even if LNT model
projection is true, since the change in cancer risk is within
the range of normal variation from year to year (see figure on
right). But they would lose the diagnostic information that
could potentially be lifesaving for the patient.
CT Dose Reduction efforts Non-diagnostic CT scans
Figures from: Goske MJ,
Strauss KJ, Coombs LP, B,
Diagnostic reference ranges for
pediatric abdominal CT.
Radiology. 2013;268:208-18.
Reproduced with permission
from RSNA (Copyright holder).
59
It is unethical to perform non-diagnostic CT scans like the one
shown (Fig. 6b) with the claim that the lower dose is reducing
cancer risk, when the claim is based on the invalid LNT model,
and even if the model is believed to be valid, the reduction in
cancer risk would be within the normal variation of cancer risk of
population from year to year (see figure on right), and so the claim
has no merit.
Non-diagnostic CT scans Quote from (Brody, 2014)
“Five percent of the CT scans using standard clinical protocols
and radiation doses below the 25th percentile were judged to be
non-diagnostic,15 suggesting that 1 in 20 paediatric abdominal CT
scans performed at some of the top institutions in the USA were
inadequate for diagnostic purposes due to excessive radiation
dose reduction efforts. This is wasted radiation exposure and,
even worse, may negatively influence care when it results in
misguided treatment based on inadequate or erroneous
information.”
60
See the comment on previous slide.
Decreased diagnostic accuracy
(Goenka, 2014)
25% dose reduction – diagnostic accuracy
maintained
50% dose reduction – unacceptable loss of
diagnostic accuracy
61
Having a 25% margin to ensure diagnostic quality is
certainly justified, when there is no validity to the claims
of increased risk of cancer from CT scans, even if the
LNT model is believed to be valid (see figure on right).
There is NO benefit to patients from
dose reduction campaign and efforts
but potential harm to patients. There
is benefit to the organizations and
individuals that perform the
campaign and efforts because of the
financial gain for performing these
potentially harmful tasks.
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Why ACR’s Dose Reduction Campaign Must be Ended In his presentation at Japan Radiology Congress 2015 entitled “We Can And We Must
Reduce Radiation Exposure: Perspective of The American College of Radiology”,
Dr. Paul Ellenbogen, ACR President, stated that
- he believes the dose-response shape for radiation-induced cancers is somewhere
between threshold response and radiation hormesis.
- there is demand for dose reduction from patients, physicians, payors, legislators, etc.
Hence ACR has ongoing dose reduction efforts in diagnostic imaging.
In view of the above shape of dose-response acknowledged by ACR President, which is
consistent with evidence discussed earlier in this presentation, there would be zero benefit
to patients from the dose-reduction efforts and there would be potential harm from the
efforts as seen in previous slides. On the other hand, there are considerable costs for the
dose-reduction and dose-monitoring efforts, which would ultimately get passed on to the
patients or the public. In view of no benefit to patients but costs and potential harm, how
can ACR justify these efforts?
The demands for dose reduction from patients, physicians, payors, legislators, etc. are
based on their misunderstanding that small doses of radiation increase cancer risk. If their
misunderstanding is corrected by providing them correct information, there would no longer
be such demands. Thus, using their demands to undertake wasteful and potentially harmful
dose-reduction efforts is not justified. These dose-reduction campaigns and efforts should
be stopped immediately. 63
• There is neither valid reason nor evidence for cancers caused by the low
radiation doses from diagnostic imaging; on the other hand, there is plenty of
evidence for reduction of cancers from low-dose radiation. Hence, dose
reduction efforts in diagnostic imaging would not benefit patients.
• Dose-reduction campaigns perpetuate the misguided cancer concerns among
patients, parents, and physicians regarding the low radiation doses from
diagnostic imaging, resulting in some physicians not ordering appropriate
studies and some patients not undergoing needed studies, delaying
diagnoses, potentially harming patients. Many patients/parents also undergo
unnecessary emotional stress due to the misguided cancer concerns
regarding scheduled or past diagnostic studies.
• Dose-reduction efforts can harm patients by misdiagnoses due to poorer
quality images.
• Dose-reduction campaigns and efforts benefit the resulting enterprises
including research while not benefiting patients and potentially harming
patients.
Hence, the definitive answer to the above question is:
No
64
Should the radiological community continue the
present radiation dose-reduction campaign and efforts?
Summary and Conclusions • LNT model is senseless, and its use results in no improvement of public health but causes
large public expenditures which provide income to LNT model proponents and resulting
enterprises including research.
• Self-interest motivated committee members to adopt the LNT model in the 1950s.
• There is plenty of evidence against the LNT model and for radiation hormesis.
• Major defects of the LNT model – ignoring adaptive response and the immune system.
• Atomic bomb survivor data – key data – no longer support the LNT model.
• Evidences quoted for low-dose radiation (LDR) carcinogenicity have dissipated.
• Children do not face increased cancer risk from low-dose radiation.
• Many publications need to be discarded and marked “Do Not Use” as they utilized older
atomic-bomb survivor data or faulty publications to justify LDR concerns.
• Research work based on the LNT model cannot be justified any longer. All the research
projects publicly funded since 2013 should be reviewed, and if any work was justified based
on low-dose radiation concerns due to the LNT model or older atomic bomb survivor data, the
project funding should be terminated, as it should not have been approved at all.
• Radiation dose concerns and dose reduction can harm patients in multiple ways:
– Patients/parents are likely refusing imaging studies and physicians not ordering proper
studies due to radiation dose concerns, placing patients’ health potentially at risk.
Patients/parents have emotional stress regarding scheduled or past diagnostic studies.
– Non-diagnostic scans are likely being performed, with one estimate of 1 in 20 pediatric
exams not being of diagnostic quality. Dose reduction efforts can harm patients from
misdiagnoses.
• Dose reduction campaigns and efforts benefit the resulting enterprises including research
while not benefiting patients and potentially harming patients.
Dose-reduction campaigns and efforts should be ended. 65
