CT Linked to Future Cancer Risk

TOPLINE:

CT examinations performed on 62 million patients in the United States during 2023 are projected to result in approximately 103,000 future cancer cases. Adults account for 91% of projected radiation-induced cancers despite higher per-examination risk in children.

METHODOLOGY:

• Approximately 93 million CT examinations are performed on 62 million patients annually in the United States, with ionizing radiation from being a known carcinogen.
• Since 2007, the number of CT examinations performed annually in the United States has increased by more than 30%, with more granular data now available describing examination types and more accurate methods for estimating organ dose.
• A risk model analysis utilized data from 121,212 CT examinations collected between January 2018 and December 2020 from 143 hospitals and outpatient facilities across 22 healthcare organizations in 20 states in the United States.
• Researchers estimated organ doses for 18 organs through Monte Carlo radiation transport simulations using examination-level technical parameters and patient size mapped to morphometry-matched hybrid computational phantoms.
• Analysis included projecting future lifetime radiation-induced cancer risk using the National Cancer Institute’s Radiation Risk Assessment Tool version 4.3.1, which utilizes risk models from the National Academy of Sciences’ Biologic Effects of Ionizing Radiation VII report.

TAKEAWAY:

• Projected radiation-induced cancers included lung cancer (22,400 cases; 90% uncertainty limits [UL], 20,200-25,000), colon cancer (8700 cases; 90% UL, 7800-9700), leukemia (7900 cases; 90% UL, 6700-9500), and bladder cancer (7100 cases; 90% UL, 6000-8500).
• Abdomen and pelvis CT examinations in adults contributed the largest proportion of projected cancers (37,500 cases; 90% UL, 32,900-42,600), representing 37% of all projected cases.
• Cancer risk per CT examination was highest in children aged under 1 year, with girls showing 20 cancers per 1000 examinations compared with 2 per 1000 in girls aged 15-17 years.
• Sensitivity analyses demonstrated the robustness of findings, with projected cancer cases ranging from 80,000 to 127,000 across different analytical scenarios.

IN PRACTICE:

“If current practices persist, CT-associated cancer could eventually account for 5% of all new cancer diagnoses annually…This would place CT on par with other significant risk factors, such as alcohol consumption (5.4%) and excess body weight (7.6%),” wrote the authors of the study.

SOURCE:

The study was led by Rebecca Smith-Bindman, MD, Department of Epidemiology and Biostatistics, University of California, San Francisco. It was published online on April 14 in JAMA Internal Medicine.

LIMITATIONS:

According to the authors, the risk model parameters are primarily based on Japanese atomic bomb survivor outcomes, raising questions about the transferability of radiation risks from the mid-20th century Japanese population to the current US population. The calculations factored in average life expectancies, potentially overestimating future cancer risk for patients who undergo CT and have shorter life expectancy due to underlying illness. Additionally, while the CT categorization algorithm was 90% accurate compared with expert review, some examinations may have been miscategorized.

DISCLOSURES:

The research was supported by awards from the National Cancer Institute, the Patient-Centered Outcomes Research Institute, and residual class settlement funds from a legal case. Smith-Bindman disclosed being a co-founder of Alara Imaging, Inc., a company focused on improving clinical and operational aspects of health systems, including radiation dose and image quality reporting for CT as part of payer-led quality programs. Additional disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.