CT Scans May Account for 5 Percent of US Cancers—Doctors Say the Story Is More Complex

CT scans can provide life-saving diagnostics—but are they also harming people?

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CT scans are essential to modern medicine, quickly diagnosing conditions from strokes to cancer. However, new research suggests that the very tool used to save lives could, in some cases, contribute to future cancer cases.

A University of California–San Francisco study estimates that CT scans performed in 2023 could lead to more than 100,000 future cancer cases—about 5 percent of annual U.S. diagnoses. That level of risk is comparable with other known factors such as alcohol and obesity.

Published in JAMA Internal Medicine, the study concludes that while CT scans remain essential, they should be used more cautiously, especially for children and patients who undergo repeated imaging.

“CT can save lives, but its potential harms are often overlooked,” Dr. Rebecca Smith-Bindman, lead author of the study and UC–San Francisco radiologist, said in a statement. “Reducing the number of scans and reducing doses per scan would save lives.”

Some experts worry that the message lacks balance and may scare patients from necessary care by emphasizing long-term cancer risks without proper context.

“It is frightening to see these numbers,” Dr. Donald Frush, pediatric radiologist at Duke University, told The Epoch Times. “But without putting them in the context of how valuable CT can be, we risk eroding public trust in a tool that saves lives every day.”

Study Scans Deeper

To estimate long-term cancer risk from CT scans, UC–San Francisco researchers analyzed a national sample of 121,212 real-world exams drawn from 143 hospitals in 20 states. The data included detailed information on scan type, radiation dose, and patient demographics.

They then used radiation risk models from the National Cancer Institute to project the number of cancers that could result from the 93 million CT scans estimated to have been performed in the United States in 2023. Their projection: about 103,000 future cancer cases—a significant increase from a 2009 estimate of 29,000.

While children face the highest risk per scan, adults account for most projected cases because of the sheer volume of imaging they receive. Abdominal and pelvic scans were the largest contributors, followed by chest, spine, and head imaging. Among children, those younger than age 1 faced the greatest individual risk—up to 20 cancers per 1,000 scans. Among adults, those aged 50 to 69 are expected to carry the largest share of future CT-related cancers.

Researchers excluded scans from patients’ final year of life, when long-term cancer risk is less clinically relevant. They also ran multiple “what-if” scenarios, with the lowest estimate at 80,000 cancers and the highest at 127,000.

According to study author Diana L. Miglioretti, the increase reflects rising CT use and more precise data on radiation exposure.

“Our projections are higher than previously reported because CT utilization has increased by 30 percent since the earlier study,” she told The Epoch Times via email.

However, some experts believe that the projections may overstate the risk. Cynthia McCollough, radiologist and medical physicist at the Mayo Clinic, questioned whether excluding only the final year of life goes far enough.

“A large portion of CT scans are performed on patients who are in the medical system for diagnosis and treatment of significant disease or injury,” she said in an email to The Epoch Times. “Including these patients in the statistical estimation of possible future cancers is flawed.”

She cited a 10-year follow-up study of patients who had undergone multiple CT exams, noting that half had died within two years, often because of the condition prompting the scan.

While the UC–San Francisco study did exclude scans from the final year of life, McCollough argued that a broader time frame would have been more appropriate, given that most radiation-related cancers take 10 to 40 years to develop.

“Following this approach would greatly decrease the number of CT-related cancers predicted by this study,” she said.

The study authors acknowledged limitations in their approach. The cancer risk models were based on data from Japanese atomic bomb survivors, which may not fully reflect the health profiles or exposures of U.S. patients. They also noted that applying average life expectancies could lead to overstating risks, since many patients who undergo CT scans are already seriously ill and less likely to develop long-term radiation-related cancers.

Smith-Bindman is a co-founder of Alara Imaging, a company that offers free software to hospitals for tracking CT radiation doses. The study notes that Alara Imaging did not participate in the research.

Understanding the Dose

Most people don’t think twice about the radiation in a CT scan. It’s fast, routine, and often feels like just another step toward answers. However, behind the speed is ionizing radiation—which, in large or repeated doses, can increase long-term cancer risk.

Radiation is a medical paradox, integrative physician Dr. Nathan Goodyear said. It can detect and treat cancer—but also, in some cases, cause it.

For most adults, a single CT scan poses low risk—about a one in 2,000 chance of developing cancer, Dr. Max Wintermark of MD Anderson Cancer Center said. For young children, it’s closer to one in 1,000 because of more vulnerable tissue and longer life expectancy.

“The radiation dose from a single CT scan is low—similar to the natural background radiation one might experience over a few years,” Wintermark said in an email to The Epoch Times. “Modern scanners have brought those doses down significantly.”

But radiation risk isn’t just about how much—it’s about what it does.

“X-rays used in CT scans cause DNA breaks,” Madan Rehani, professor of radiology at Harvard Medical School, told The Epoch Times in an email. “Those breaks that do not get repaired or are misrepaired have the potential to lead to cancer many years after they have occurred.”

CT scan radiation can increase cancer risk by damaging DNA, causing mutations, and disrupting cell growth, Miglioretti said. It can also affect nearby cells and trigger oxidative stress, further promoting cancer over time.

While one scan may be fine, many people don’t stop at one. Repeat imaging can cause radiation exposure to add up quickly. The risk then shifts from hypothetical to more substantial, especially if older machines or outdated protocols are used, which often deliver higher doses than modern, optimized systems.

A Tool That Both Helps and Harms

The UC–San Francisco study has renewed concern over radiation exposure, but many experts stress the need to weigh those risks against CT scans’ life-saving benefits.

“Never refer to how many cancer cases CT is responsible for without referring to how many cancer (and other) cases CT is helping to reduce or cure,” Marc Kachelriess, professor at the German Cancer Research Center, told The Epoch Times via email. “Never risks without benefits! Never cons without pros!”

Others take issue with the study’s comparisons. Some experts argue that likening CT scans to well-established lifestyle risks may mislead the public. McCollough called the comparison to alcohol and obesity inappropriate.

“We have hard data demonstrating the link between alcohol, excess body weight, and poor health outcomes,” McCollough said. “No such data exist for CT. Suggesting that diagnostic radiation is on par with those risk factors is inappropriate and unsupported by the evidence.”

She said current estimates rely on models, not direct causal proof.

“These studies don’t prove any causal effect between CT scans and cancer incidence,” she said. “Until we have stronger data, such claims should be considered highly speculative.”

The debate centers on the balance between harm and healing. Frush said he agrees that the risks are real, but believes that studies such as UC–San Francisco’s lean too heavily on fear.

“These articles scare people,” Frush told The Epoch Times. “What doesn’t come through is the overwhelming value and life-saving part of what CT is. The fact is, every day, those who do it can say this is a really helpful thing we did.”

The American College of Radiology (ACR) also responded to the study, cautioning that its cancer projections are based on statistical modeling rather than patient outcomes. While acknowledging theoretical risks, the group emphasized that no published research has directly linked CT scans, even repeated ones, to cancer.

“Medical imaging exams—including CT—are a primary factor in declining cancer death rates,” the ACR said.

Study researchers pushed back on the ACR’s claim that there is no direct link between CT scans and cancer.

“Many studies have provided direct evidence of cancer risks associated with CT imaging,” Miglioretti said. “It seems the ACR has not fully considered the recent evidence.”

She pointed to two large 2023 studies—one in Nature Medicine that linked CT radiation to increased rates of blood cancers, and another in Lancet Oncology that found elevated risks of brain tumors in children and young adults following CT exposure.

In many cases, that is true. CT scans are unmatched for speed and detail, particularly in emergencies. They can detect strokes, guide trauma care, or quickly identify internal organ damage. In these moments, waiting for a lower-dose alternative such as MRI or ultrasound simply isn’t an option, Frush said.

Miglioretti said: “Patients and providers should consider how the results of a CT scan will inform clinical decision-making and whether alternative imaging options that do not involve radiation are available. When a CT scan is medically necessary, the radiology team should ensure that radiation doses are kept as low as possible for the specific clinical indication.”

The Debate Over Overuse

Some in the medical community say that too many CT scans are ordered out of habit, caution, or fear of lawsuits. Dr. Richard Semelka, radiologist and longtime advocate for safer imaging, sees overuse as a systemic issue.

“A study reported 30 percent of imaging studies are unnecessary,” he said in an email to The Epoch Times, noting that this figure “has been a consistent number for decades.”

He believes that deeper forces are at play—such as defensive medicine, financial incentives, and a fast-paced health care system in which physicians may order a scan to be thorough or to save time.

“CT is used as a fast extension of the medical exam,” he said. “Health care workers have to spend more time seeing patients.”

However, not everyone agrees that the problem is so clear cut.

Frush said calling CT use “overuse” oversimplifies the complexity behind those decisions.

“The blanket statement that we’re doing way too many unnecessary examinations is a complete disservice to the patients and their physician’s decision about what to do, because it’s generally a shared decision,” he said.

Imaging decisions are nuanced. A patient may request a scan for reassurance. A doctor may want to rule out worst-case scenarios. Some symptoms fall into diagnostic gray areas.

Frush gave an example: patients with persistent headaches, fearing a brain tumor.

“Knowing that their head CT is normal is incredibly important for their health,” he said. “What doesn’t come through is that particular patient scenario.”

What may seem unnecessary from a distance can be deeply meaningful in a clinical room, illustrating the disparity between public health caution and individual care.

The Push for Safer Scans

Even as CT scans remain a vital tool, momentum is growing to make them safer through design and policy.

In January, the Centers for Medicare & Medicaid Services issued rules requiring hospitals to track and report CT radiation doses. Starting in 2027, noncompliant facilities could face penalties. The rules also aim to improve oversight of scan use and image quality.

However, experts said real change also depends on the manufacturers of the machines.

Rehani, a global radiation safety expert, believes that CT makers can lower radiation doses—but only if buyers demand it.

He noted that when manufacturers are asked why they haven’t produced such scanners, they often respond that hardly any buyers request them. Rehani believes that if buyers of CT scanners push the industry, it could lead to significant dose reductions, allowing patients to undergo multiple scans without the current level of risk.​

“The industry has been reducing CT scan dose for the past two decades, but the question is, ‘Is that enough?’” Rehani asked. “We want to see a day when patients should not have to worry about radiation risk while undergoing a CT scan.”

He isn’t alone. Many in the field argue that the technology exists, but without stronger market pressure or regulation, progress has been uneven.

Many larger hospitals are investing in ultra-low-dose scanners and software that adjusts doses per patient. However, many smaller facilities haven’t caught up, and expecting them to may not be realistic.

“Out in rural America, that level of care doesn’t exist,” Frush said. “The radiologist at a small clinic who reads one pediatric CT every two months may not have the same resources or expertise as someone at a major children’s hospital, and that needs to be considered when we talk about national standards.”

Ultimately, experts said it will take a combined push from regulators, hospitals, and equipment makers to ensure that the scans we rely on are as safe as they are effective—without leaving smaller providers behind.

A Conversation That Rarely Happens

For many patients, CT scan risks rarely come up in conversation.

“They’re not happening as much as they could be,” Frush said. He pointed to a key challenge: short appointments and physicians who often lack training in radiation risks. That silence leaves many patients and parents unaware of the trade-offs.

“It’s not that it’s unimportant,“ Frush said. ”It’s just impossible to cover everything in today’s health care setting.”

Semelka, a longtime advocate for safer imaging, put it bluntly.

“Absolutely not,” he told The Epoch Times when asked if patients are adequately informed about the risks of radiation. “This should be mandatory by government regulations.”

The lack of transparency can also breed false reassurance.

“People assume if Medicare and Medicaid recommend it in protocol, then it must be safe,” Goodyear said.

The risks are even greater for children, yet few parents receive a clear explanation of options.

“Few patients and their families are counseled about the risk associated with CT examinations,” UC–San Francisco study co-author Dr. Malini Mahendra said in the statement.

Frush agreed that conversations need to improve, but said they also need to be flexible.

“There’s no one-size-fits-all script,” he said. “Some patients want every detail. Others want only the bottom line. But both deserve informed, respectful care.”

What Patients Can Do

Navigating medical imaging can be daunting, especially when weighing the benefits of early diagnosis against the long-term risks of radiation. But experts agree: Patients are not powerless.

Today’s imaging tools can dramatically reduce exposure, particularly for children. At the Mayo Clinic, McCollough’s team has developed pediatric CT protocols that use doses as low as those of a routine chest X-ray.

National campaigns such as Image Gently and Image Wisely—launched by the ACR and supported by experts such as Frush—encourage clinicians to minimize radiation and order scans only when necessary.

“Families should have no fear about a needed CT scan but should have concern from an avoidable CT scan,” Rehani said. It’s about knowing when the scan is truly necessary.

The first step, Goodyear said, is to ask questions. Patients and parents should feel empowered to speak up. Some key questions include:

• What are we trying to learn from this scan?
• Are there alternatives, such as MRI or ultrasound, that don’t use radiation?
• Is this scan urgent, or could we wait?
• Has the dose been adjusted for my child’s size?

Even a brief conversation can influence care. When patients raise concerns about radiation or alternatives, doctors often pause and reconsider.

If there’s uncertainty, a second opinion is always an option.

While some parents may hesitate to question a doctor’s recommendation, Goodyear encourages them to do so.

“Parents are the best advocates for their children, period,” he said.

Ultimately, experts agree that CT scans are vital tools, but that they must be used thoughtfully and with informed consent.