SAN FRANCISCO (Diya TV) — Computed tomography (CT) scans, a cornerstone of modern diagnostic medicine, may be contributing to more cancer cases than previously believed, according to new research led by scientists at the University of California, San Francisco. The study, published April 14 in JAMA Internal Medicine, estimates that radiation from CT scans performed in 2023 could eventually account for about 5% of all new cancer cases annually in the United States.
That estimate is based on a risk model developed by UCSF researchers, who analyzed data from 93 million CT scans conducted on 62 million patients in 2023. The model projects that these scans will result in approximately 103,000 future radiation-induced cancers over the lifetimes of the patients exposed.
“This puts CT scans on par with other major cancer risk factors like alcohol consumption and excess body weight,” said lead author Dr. Rebecca Smith-Bindman, a UCSF radiologist and professor of epidemiology. “The goal is not to scare patients, but to help them make informed decisions about whether and when a CT is truly necessary.”
CT scans expose patients to ionizing radiation, a known carcinogen. While a single scan generally carries a low risk, cumulative exposure, especially among patients with chronic conditions like Crohn’s disease, can add up significantly. Smith-Bindman emphasized the importance of discussing potential risks and benefits with physicians before proceeding with imaging.
The study utilized data from UCSF’s International CT Dose Registry, which includes a multicenter sample of CT exams across 17 hospital systems. Researchers calculated organ-specific radiation doses by patient age, sex, and scan type, then scaled their findings to represent national figures. They based their cancer risk estimates on the National Academy of Sciences’ Biological Effects of Ionizing Radiation VII report, which draws from long-term data on atomic bomb survivors in Japan.
Notably, adults accounted for 93,000 of the projected 103,000 cancers, due to higher overall CT usage, even though children and adolescents face a greater risk per scan. Infants under one year old are especially vulnerable, facing a 10-fold increase in risk, said study co-author Dr. Malini Mahendra, a UCSF pediatrician.
The most common projected cancers include lung cancer (22,400 cases), colon cancer (8,700), leukemia (7,900), and bladder cancer (7,100). Among women, breast cancer ranked the second most common, with 5,700 projected cases. The highest-risk scans were of the abdomen and pelvis, which alone may account for 37,500 cancer cases, followed by 21,500 cases linked to chest CTs.
The use of CT scans in the U.S. has surged by 35% since 2007, growing from 68.7 million scans to 93 million in 2023. That rise, researchers say, can’t be explained by population growth alone. Financial incentives, time constraints, and the perception that more imaging equals better care may all contribute to overuse.
“Sometimes it’s just faster to order a test than to have a lengthy conversation with the patient,” Smith-Bindman said. Additionally, the lack of standardized radiation dosing means patients can receive widely varying doses for the same scan at different hospitals. The study found that about one-third of scans exceeded the recommended maximum radiation thresholds set by the Centers for Medicare and Medicaid Services (CMS) and UCSF.
In an accompanying editorial, Dr. Ilana Richman of Yale School of Medicine and Dr. Mitchell Katz of NYC Health + Hospitals acknowledged some uncertainty in the estimates, but said the findings highlight a clear need for caution. They advocated for reducing CT use in low-risk patients, encouraging alternatives like ultrasound and MRI, and better educating both providers and patients.
“CT is inextricably woven into the fabric of modern medicine,” they wrote. “But like all powerful tools, it must be used wisely.”
Smith-Bindman and her colleagues called for greater transparency, dose standardization, and thoughtful justification of every CT scan. “We hope this data prompts meaningful conversations between doctors and patients about whether a CT is truly necessary — and if safer alternatives might suffice,” she said.
