Cancer Risk from Low Dose Radiation of CT Scan May
Be Solved by Epigentics or NIH Study
Two reports in radiology journal: Epigenetics may
determine risk of low-dose radiation... and explain mechanisms of aging,
human development, and the origins of cancer, heart disease, mental
illness, etc.
Feb. 1, 2010 Concern about the cancer risk from
low level radiation, particularly low-dose radiation delivered from
computed tomography (CT) scans, has been growing in the medical
community. Some suggest that about 1.5 to 2 percent of all cancers in
the USA might be caused by the clinical use of CT. A new study by NIH
and the possibility of epigenetics to better understand this risk are
two of the reports in the February issue of the Journal of the
American College of Radiology (JACR).
There remains a lack of consensus amongst the
medical and scientific communities about any cancer risk from low level
radiation, says one of these reports, that says the study of epigenetics
may play a role in determining whether or not future trends of diseases
can in fact be linked to utilization of CT.
The term epigenetics refers to changes in the
phenotype (appearance) or gene expression caused by mechanisms other
than changes in the underlying DNA sequence. These changes may remain
through cell divisions for the remainder of the cell's life and may also
last for multiple generations.
"Radiation safety is, without a doubt, a large
concern for practicing radiologists today," said Shella Farooki, MD,
author of the article and radiologist and director of research for
Columbus Radiology Corp in Columbus, OH.
"However, the current focus does not account for
the possibility of harm to future generations from radiation delivered
today. I believe that it is equally, if not more important, to consider
potential harm to the patient's offspring and their offspring's
offspring," she said.
"The effects of ionizing radiation have been
demonstrated in neighboring cells (non-targeted radiation), known as the
bystander effect. In addition, ionizing radiation effects have been
shown to span generations, resulting in heritable defects in mice.
However, we need to bridge the gap between understanding the epigenome
functionality and radiation exposure before assuming anything," said
Farooki.
"In 2008, the National Institutes of Health (NIH)
announced that $190 million had been earmarked for epigenetics research
over the next five years," she said.
In announcing the funding, government officials
noted that epigenetics had the potential to explain mechanisms of aging,
human development, and the origins of cancer, heart disease, mental
illness, as well as other conditions.
"Epigenetics may ultimately turn out to have a
greater role in health and disease and treatment of genetics itself; and
given this knowledge, one wonders if future trends in diseases will be
linked to today's utilization of CT," said Farooki.
"Clearly, long term epidemiological studies are
needed to answer this question, but in the meantime, we are faced with
the continued struggle of radiation risk versus benefit," she said.
NIH takes step to assess any possible risk
associated with low-dose radiation exposure
The second article reports that researchers at the
National Institutes of Health (NIH) Clinical Center are incorporating
radiation dose exposure reports into the electronic medical record, an
effort that they hope will lead to an accurate assessment of whether any
cancer risk is associated with low-dose radiation exposure from medical
imaging tests.
The electronic medical record allows for the
storage, retrieval, and manipulation of one's medical records.
There is much controversy surrounding diagnostic
medical radiation exposure. "One widely publicized appraisal of medical
radiation exposure suggested that about 1.5 to 2 percent of all cancers
in the USA might be caused by the clinical use of CT alone," said David
A. Bluemke, MD, lead author of the article and director of Radiology and
Imaging Sciences at the NIH Clinical Center.
"Since there is no epidemiologic data directly
relating CT scanning to cancer deaths, scientific assessment must
instead rely on the relationship between radiation exposure and death
rates from Japanese atomic bomb survivors. While the legitimacy of this
approach remains debated, radiologists as well as clinicians may
rightfully be confused by the ongoing controversy. Patients seeking
medical help may legitimately question the rationale of, and any risks
from, diagnostic radiology tests."
Radiology and nuclear medicine at the NIH Clinical
Center have developed a radiation reporting policy that will be
instituted in cooperation with major equipment vendors, beginning with
exposures from CT and PET/CT.
"All vendors who sell imaging equipment to
Radiology and Imaging Sciences at the NIH Clinical Center will be
required to provide a routine means for radiation dose exposure to be
recorded in the electronic medical record. This requirement will allow
cataloging of radiation exposures from these medical tests," said
Bluemke.
In addition, radiology at NIH will also require
that vendors ensure that radiation exposure can be tracked by the
patient in their own personal health record. This approach is consistent
with the American College of Radiology's and Radiological Society of
North America's stated recommendation, that "patients should keep a
record of their X-ray history."
"The cancer risk from low-dose medical radiation
tests is largely unknown. Yet it is clear that the U.S. population is
increasingly being exposed to more diagnostic-test-derived ionizing
radiation than in the past," according to Bluemke.
"While these steps themselves are not sufficient to
allow population-based assessment of cancer risk from low-dose
radiation, they are nonetheless necessary to begin a data set for this
determination. The accumulation of medical testing doses of hundreds of
thousands of individuals in the United States over many years will
ultimately be necessary. We encourage all medical imaging facilities to
include similar requirements for radiation-dose-reporting outputs from
the manufacturers of radiation-producing medical equipment," Bluemke
said.
About information source:
The February issue of JACR is an important resource
for radiology and nuclear medicine professionals as well as students
seeking clinical and educational improvement.
For more information about JACR, please visit
www.jacr.org.
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Feb. 1, 2010 Concern about the cancer risk from
low level radiation, particularly low-dose radiation delivered from
computed tomography (CT) scans, has been growing in the medical
community. Some suggest that about 1.5 to 2 percent of all cancers in
the USA might be caused by the clinical use of CT. A new study by NIH
and the possibility of epigenetics to better understand this risk are
two of the reports in the February issue of the Journal of the
American College of Radiology (JACR).