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Patient Safety Tip of the Week
CT Scans and
Cancer Risk
We’ve often discussed the risks of radiation,
with regard to future development of cancer (see list
of prior columns below). And, while any imaging study using ionizing radiation
can increase the cancer risk, the major contributor to that risk is CT
scanning. The cumulative dose of radiation over a lifetime is critical and children
who receive multiple CT scans are most vulnerable.
Rebecca Smith-Bindman, MD has been one of
the foremost critics of excessive radiation attributed to CT scanning and has
published with her colleagues some of the seminal papers regarding CT scanning
and cancer risk. Now, Smith-Bindman and colleagues have again published an
important study on the issue (Smith-Bindman
2025).
The researchers used the National Cancer
Institute’s Radiation Risk Assessment Tool to project future lifetime
radiation-induced cancer risk. They concluded that, if current practices
persist, CT-associated cancer could eventually account for 5% of all new cancer
diagnoses annually.
Note that the estimates are theoretical and
are based on cancer risks that were associated with Japanese atomic bomb
survivor outcomes.
An estimated 61,510,000 patients underwent
93,000,000 CT examinations in the US in 2023, including 4.2% in children. Using
that risk assessment tool, the authors projected approximately 103,000
radiation-induced cancers would result from these examinations (range 80,000 to
127,000). Though children and adolescents are at greatest risk, adults account
for most of the radiation-induced cancers, largely because of the greater
volume in adults.
They projected that lung cancer, colon
cancer, leukemia, and bladder cancer to be the most common radiation-induced
cancers (breast cancer would be the second most common cancer in women).
CT scans of the abdomen, pelvis, and chest would
be the scans contributing the most to the increased cancer risk.
The authors note that this projected number
of radiation-induced cancers is 3 to 4 times higher than an earlier assessment
of CT exposure for several reasons: increased CT utilization, better
calculation of dose given, and multiphase scanning.
The authors posit that “justification of use
and optimization of dose, including consideration of the need for multiphase
examinations, are the tenets of CT imaging and must be applied uncompromisingly
to mitigate potential harm.”
The American College of Radiology (ACR)
issued a message in response to publication of the Smith-Bindman study (ACR
2025) noting that the
projections are not based on actual patient outcomes and cautioned patients
that both the benefits and risks of CT scanning should always be considered. They
recommend that patients, before undergoing any imaging study involving
radiation, should ask their physician or other medical provider the following
questions:
·
How will having this exam improve my health
care?
·
Are there alternatives that do not use radiation
which are equally as good (e.g. MRI, ultrasound, etc.)?
·
Is this facility ACR Accredited (which ensures
high quality standards, including regular surveys of the equipment by medical
physicists, certified technologists performing the exams, and interpretation by
radiologist physicians who meet stringent education and training standards)?
They also recommend that patients should
keep a record of their (or their loved ones’) imaging procedures. They also
note that the ACR co-founded the Image Gently® and Image Wisely®
initiatives to help providers avoid ordering low value imaging and optimize
radiation dose used in many scans.
Ensuring that a CT scan is necessary is the
first step. Undoubtedly, many CT scans are done as “low value” studies. Use of
clinical decision rules, such as the many clinical decision rules for
performing head CT scans after minor trauma (see list of columns below) may be
helpful. Understanding when alternative imaging studies may provide appropriate
diagnosis without ionizing radiation is also important. Many pediatric patients
still get CT scans for suspected appendicitis, when ultrasound examinations
would likely provide the desired answer. Clinical decision support at the time
of order entry is a logical tool to reduce ordering the wrong study but it has
yet to demonstrate solid results. And better guidelines for the frequency of
“follow up” CT scans would be important.
Closer attention to radiation dose and
better protocol design may lower the cancer risk.
Attention to the cumulative dose of
radiation is important. A clinician may have no idea how much radiation a
patient has had in the past. We like the ACR recommendation that patients keep
their own record of prior imaging studies (or that of their children or other
loved ones).
Sometimes, good intentions also contribute!
A clinician might order a CT scan instead of an MRI scan because he/she thinks
that is the more cost-effective approach. Yet, in many such cases, that leads
to “layering” where a patient ends up getting both a CT scan and an MRI scan.
Sometimes the policies of insurers may also be problematic. For example, some
insurers require prior authorization for MRI scans but not CT scans, so a
clinician might order the CT scan to avoid the hassle of getting prior
authorization.
And a tough nut to crack is patient demand.
We still see patients expecting to get an imaging study.
Not only do unnecessary CT scans add to our
already bloated healthcare costs, but the Smith-Bindman study is a reminder
that the costs of unnecessary CT scans is more than
just financial.
Some
of our previous columns on the issue of radiation risk:
·
February 2, 2010 “The
Hazards of Radiation”
·
November
23, 2010 “Focus on Cumulative Radiation Exposure”
·
March 2010 “More
on Radiation Safety”
·
June 2011 “Progress
in Reducing Radiation from CT Scans”
·
April
2013 “Radiation Risk of CT Scans: Debate Continues”
·
June 4,
2013 “Reducing Unnecessary CT Scans”
·
July
2013 “More on the CT/Cancer Debate”
·
January
2017 “Still
Too Many CT Scans for Pediatric Appendicitis”
·
November
2017 “SCANSMART
Program to Use CT Safely in Children”
·
June 2023 “Childhood
CT Scans and Cancer Risk”
Some
of our previous columns on CT scans in minor head trauma:
April 16, 2007 “Falls
With Injury”
July 17, 2007 “Falls
in Patients on Coumadin or Heparin or Other Anticoagulants”
March
2010 “CATCH: New Clinical Decision Rule for CT in
Pediatric Head Trauma”
November
23, 2010 “Focus on Cumulative Radiation Exposure”
June
5, 2012 “Minor Head Trauma in the Anticoagulated
Patient”.
July
8, 2014 “Update: Minor Head Trauma in the
Anticoagulated Patient”
January
2017 “Still
Too Many CT Scans for Pediatric Appendicitis”
March
2017 “Update
on CT Scanning after Minor Head Trauma”
September
2017 “Clinical
Decision Rule Success”
August
21, 2018 “Delayed
CT Scan in the Anticoagulated Patient”
September 21, 2021 “Repeat CT in Anticoagulated
Patients After Minor Head Trauma Not Cost-Effective”
December 14, 2021 “Delayed Hemorrhage After
Head Trauma in Anticoagulated Patients”
August 2022 “CDSS
Success for Pediatric Head CT”
February 2024 “Another
Canadian Head CT Rule”
References:
Smith-Bindman R, Chu PW, Azman Firdaus H, et
al. Projected Lifetime Cancer Risks from Current Computed Tomography Imaging.
JAMA Intern Med 2025; Published online April 14, 2025
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2832778
ACR (American College of Radiology). ACR
Statement on JAMA CT Scan Radiation Study (Smith-Bindman, et al). Newswise 2025;
April 14, 2025
https://www.newswise.com/articles/acr-statement-on-jama-ct-scan-radiation-study-smith-bindman-et-al
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