New cancer risk data suggests pause on CT scan

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Hello. I am Dr. David Johnson, professor of medicine at Eastern Virginia Medical College and Old Dominion University in Norfolk, Virginia.

The risk of lifespan cancer from CT scans is increasing. This was previously highlighted in the paper, Released in 2014commissioned by the American Gastroenterology and the World Gastroenterology Organization. Radiation exposure physicians, care providers, patients and recommended strategies to mitigate them.

Ionizing radiation is recognized as a carcinogen by the US Food and Drug Administration, whether it is medical or non-medical. The designation is based on findings establishing lifetime incremental risks among individuals exposed to the Nagasaki and Hiroshima atomic bombs, and across several longitudinal databases from occupational or environmental exposure.

The outcome of ionizing radiation exposure can be divided into two effects: deterministic and probabilistic. Deterministic effects are those observed by radiation oncologists when using ionizing radiation to attack cancer and seeing immediate effects such as skin necrosis. Stochastic effects occur over time and are sided in that they are not clear, but perhaps revealed over decades. The stochastic effect is the focus of this discussion.

This stochastic effect is perhaps most obvious in younger patients exposed to radiation.

2006 National Academy of Sciences Report I estimated that A single dose of 10 MSV was essentially an exposure seen on abdominal CT scans, and was associated with an estimated lifetime risk of developing solid cancer or leukemia in about 1000 people.

a 2007 Review in New England Journal of Medicine Cancer risk associated with radiation exposure was also assessed, but was defined as occurring over time. Young patients reported three times more likely to have cancer-related death based on radiation exposure. That is where the stochastic effects that occur over time make a difference.

Estimated risk has shifted slightly with the latest data.

Previously, it was estimated that about 1% of new cancers were due to radioactive exposure. However, the use of CT scans increased logarithmically over the years between them, from 3 million in 1980 to 72 million in 2007. 93 million The latest data for 2023 shows that these substantial increases cannot be explained by the increase in people all over the world, as the population is independent.

Impressive predictions for new risk models

Previous risk assessments relied on relatively undefined models.

in New research Published in Jama Internal MedicineHowever, the researchers developed a risk model using patient-level data extracted from CT scans performed at 143 US hospitals and outpatient facilities related to 22 healthcare facilities in 20 states, representing very widespread exposure. We then looked at approximately 120,000 CT scans performed at the University of California, San Francisco in both the pediatric population and adults.

This information was collectively used to model future lifetime radiation-induced cancer risk using Monte Carlo simulations. They ruled out trials that occurred last year with CT scans related to life, PET scans, and any interventions or biopsies that increased radiation exposure.

Their discoveries were very impressive.

Age-adjusted estimates of the risk of radiation-induced cancer increased over time in children, representing only about 5% of the total CT scans performed in 2023. breast cancer. This is an important consideration when starting to talk about pediatric exposure.

Adult CT scans accounted for 95% of the trials.

Among all age groups, CT scans were associated with an increase in predicted numbers of over 22,000 new lung cancers, 8,700 new cases. Colon cancerapproximately 8,000 new cases of leukemia, and 7,100 new cases Bladder cancer.

Breast cancer is the second most common among female patients of all ages, accounting for 5,700 new cases.

The largest predicted cancer was due to abdominal and pelvic CT scans in adults, accounting for approximately 37% and 32% of all CT scans, followed by 21% of the chest CT scans, respectively.

Interpreting these data presents several challenges. One potential limitation is that researchers used average life expectancy. This means that patients undergoing CT scans may have shorter life expectancy due to underlying illness.

However, the numbers reported here are particularly higher than previous estimates. This new analysis reflects a higher combination of physical domain and CT categories with clinical signs (18 in adults and 13 in children) and is more specific. Analysis suggests that CT scans can be responsible for 1% to 5% of clinical cancer each year.

What does that mean in the future?

CT scan is a great technology. There is no doubt about that. However, you may want to consider potential alternatives.

You might also want to ask yourself whether these scans are the best tools we have and whether they will ultimately change patient management.

In the past, there have been several initiatives directed at the creation of smart cards, which have led patients to continue assessments of cumulative radiation doses and exposure. This effort has not been actually ruled out, but remains on the radiologist's to-do list to change the pattern of what they consider potentially radioactive cancer-related risks.

A few years ago I co-authored Opinion piece It argues that CT scans or radiation exposure should be subject to an informed consent process that requires patients to speak about risks, benefits, and alternatives. This is similar to discussions with patients about other procedures and procedures.

Patients need to be aware of the associated risks of CT scans, and care providers ordering them must be increasingly sensitive to the fact that they may have a stochastic effect.

So my plea is to press the pause button when ordering a CT scan. Ask if that really is the best benefit of the patient.

I am Dr. David Johnson. Thank you for listening.

Medscape's regular contributor, David A. Johnson, MD, is a professor of medicine and chief of gastroenterology at East Virginia Medical College in Norfolk, Virginia, and a former president of the American College of Gastrointestinal Sciences. His main focus is gastroenterological clinical practice. He has been interested in major research in esophageal and colon diseases and has recently published extensively in the internal medicine/gastroenterology literature with the effects of sleep and microbiota on gastrointestinal health and disease.