Do Medical Scans Really Increase Cancer Risk? Latest Findings

Computed tomography (CT) scans are now a common part of modern medical practice. In France, approximately 15 million CT scans were performed in 2022, according to Eurostat. In a matter of minutes, they can be used to examine the brain after an injury, confirm a pulmonary embolism, detect a tumor, or investigate unexplained pain.

However, this performance relies on the use of X-rays, and therefore ionizing radiation. It’s well established that exposure to ionizing radiation, at high doses, increases the risk of cancer. The risk at lower doses, such as those received during medical imaging, is more difficult to measure, but This proves not nonexistent.

CT Scans and Cancer Risk: A New Study Fuels the Debate

On April 14, 2025, JAMA Internal Medicine published a modeling study estimating the exposure of Americans to CT scans in 2023. Researchers estimated:

• 93 million CT scans were performed
• 61.5 million patients were involved
• Approximately 103,000 cancer cases induced by radiation are projected over a lifetime (90% interval: 96,400 to 109,500).

These figures are based on average doses administered and risk models derived from epidemiological data. In other words, this is a statistical projection, not a count of observed cancers. The study does not claim that a single scan causes cancer, but rather evaluates an overall risk at the population level.

The authors also estimate that, if current practices remain unchanged, CT scans could account for up to 5% of all new cancer diagnoses per year in the United States.

What are Ionizing Radiation and its Risks?

CT scans utilize X-rays, a form of ionizing radiation. These radiations have the ability to remove electrons from atoms. At high doses, this can damage the DNA within cells. If these lesions are not properly repaired, they can, theoretically, contribute to the development of cancer years later. It is important to distinguish between two situations:

• High doses, such as those received during nuclear accidents or in radiation therapy.
• Low, repeated doses, such as in medical imaging: the risk is more difficult to measure directly and often relies on statistical models.

It is this second case that fuels the debate.

A Low Risk at the Individual Level

A CT scan does not automatically cause cancer. The probability that a single examination will lead to a cancerous disease is very low. It is the accumulation of examinations, on a population-wide scale, that can become significant.

The American study shows that the most “contributing” examinations in terms of projected risk are those of the chest, abdomen, and pelvis.

Certain organs may be more affected in statistical projections: the lungs, colon, leukemia, and, in women, the breast. But again, these are probabilistic calculations.

Are Children More Sensitive?

Children are indeed more sensitive to ionizing radiation. Their bodies are growing, their cells are dividing more rapidly, and their longer life expectancy allows more time for a potential cancer to develop.

French publications specializing in radiology emphasize that vigilance is particularly important in pediatrics. Radiologists adjust doses to children’s body types and, when possible, prefer ultrasound or MRI, which do not use ionizing radiation.

A Benefit-Risk Balance at the Heart of the Decision

Medicine does not function without compromise. Every procedure carries a benefit and a risk. In the case of the CT scan, the balance overwhelmingly favors the benefit when it is justified. Diagnosing a stroke quickly, identifying internal bleeding, confirming a pulmonary embolism… In these situations, a CT scan can save a life. The theoretical long-term risk then becomes secondary to the immediate urgency.

The principle of radiation protection applied in France rests on two pillars:

• Justification: Performing a CT scan only when it is necessary.
• Optimization: Using the lowest possible dose compatible with an exploitable image.

This is known as the ALARA principle (“As Low As Reasonably Achievable”). In France, population exposure to medical imaging procedures is closely monitored by the Nuclear Safety Authority (ASN) and the Institute for Radiological Protection and Nuclear Safety (IRSN).

Are There Too Many CT Scans?

According to the Nuclear Safety Authority, the number of CT scans increased by approximately 11% between 2017 and 2022. This increase in the number of examinations is linked to several factors:

• Improvements in equipment
• Easier access to imaging
• Increased diagnostic demands
• “Defensive” medicine in the face of medico-legal risk.

The American study does not conclude that there is abusive use, but it invites reflection on practices. In France, radiological societies regularly emphasize the relevance of prescriptions. The goal is not to reduce access to CT scans, but to avoid redundant or unhelpful examinations.

IMPORTANT NOTE

According to the IRSN, medical imaging examinations account for approximately 40% of the total exposure of the French population to ionizing radiation. CT scans alone account for nearly 70% of this medical dose.