Radiology from CT scans could contribute to more than 100K new cancer cases in U.S. each year

The current use and dosage of computed tomography (CT) exams in the U.S. could result in 103,000 future cancer diagnoses in the United States, a new modelling study predicts. If the number of annual CT exams stays the same, they could contribute to 5% new cancer diagnoses a year. The number of CT exams has been rising in the U.S., with a 30% increase in use since 2009, when Archives of Internal Medicine published a similar analysis. Researchers from the U.S. and the U.K. examined 93 million CT exams performed in 62 million U.S. patients in 2023, calculating that 103,000 excess cancers would result from these CT scans. The model predicted these cancers would include: 21,400 cases of lung cancer (with a higher incidence in female patients)8,400 cases of colon cancer7,400 cases of leukemiaFour per cent of the CT scans were in children, leading the modelling to suggest the imaging would result in 9,700 more cancers in those children’s lifetimes. These were predicted to include: 3,500 cases of thyroid cancer (higher in female patients)990 cases of lung cancer630 cases of breast cancerThe model showed that reducing the dose by 20% would drop future CT-related cancer cases by 22.2%. Raising it would increase CT-related cancers by 23.3%.“These future cancer risks can be reduced either by reducing the number of CT scans (particularly low value scans which are used in situations where they are unlikely to help the patient) or by reducing the doses per exam,” said Dr. Rebecca Smith-Bindman, co-lead author and a radiologist and professor of epidemiology and biostatistics, obstetrics, gynecology and reproductive Medicine at the University of California San Francisco in a press release from the U.K.’s Institute for Cancer Research. “The doses for CT remain highly variable across patients’ hospitals, even in the U.K, and there are opportunities to reduce those doses without reducing the accuracy of the tests.”When CT exams are used in a clinically appropriate context, the risks outweigh the benefit, notes co-lead author Amy Berrington, lead of the clinical cancer epidemiology group at the Institute for Cancer Research (ICR) in London. When the CT-related cancer risks are seen at the population level, the full impact of CT use is evident. “While the NHS in the U.K. has a much better system to ensure that CT scans are clinically justified, we must not get complacent. Many other countries in Europe and also Australia perform high numbers of scans—and these numbers are rising,” Berrington said in the ICR press release. “We are urging doctors to ensure that scans are only carried out where necessary, and that doses are appropriate for the patient.”The modelling is based on the National Academy of Sciences Biologic Effects of Ionizing Radiation (BEIR) VII report for site-specific cancers. They adjusted for various factors, including age, sex and dose. The researchers excluded any scans performed in the last year of life.The model is specific for the United States, where use of CT exams is high. In Canada, there were 160.2 CT exams per 1,000 people in 2022 to 2023, a report by Canada’s Drug Agency (formally CADTH) states. These were in publicly-funded facilities; some private facilities do offer CT scans. In the U.S., there were 254.6 CT exams per 1,000 in 2021, the second highest rate of CT exam use in Organisation for Economic Cooperation and Development (OECD) countries. The top was by South Korea with 281.5 CT exams per 1,000.A 2019 study published in JAMA Pediatrics found that Canadian emergency departments used CT scans of the head and abdomen significantly less in children than emergency departments in the U.S. The used of abdominal CT scans in children was 10-fold higher in the U.S. compared to Canada. The study, led by Dr. Eyal Cohen of the Hospital for Sick Children in Toronto, found no difference in outcomes, suggesting imaging use in the U.S. could be reduced.Choosing Wisely Canada has a list of eight tests and treatments to question in radiology, including the recommendation to consider ultrasound before conducting a CT scan for cases of suspected appendicitis in children.The new study is published in JAMA Internal Medicine.

Radiology from CT scans could contribute to more than 100K new cancer cases in U.S. each year

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