American College of Radiology criticizes prominent study claiming CT imaging causes cancer

The American College of Radiology on Monday criticized new research claiming that CT exams can cause cancer. 

Scientists published the investigation in JAMA Internal Medicine on April 14, projecting lifetime cancer incidence associated with the common imaging exam. They concluded that—if current radiation dosing and utilization practices continue—radiation exposure from CT could eventually account for 1 of every 20 new cancer diagnoses annually. 

ACR issued its rebuttal mid-Monday, noting that the “theoretical radiation risk proposed” by the study authors is “not based on actual patient outcomes.” Even with increased CT use, advances in technology and the optimization of imaging protocols have reduced the population radiation burden, according to the National Council on Radiation Protection and Measurement. 

“There are no published studies directly linking CT scans (even multiple CT scans) to cancer,” ACR said April 14. “Americans should not forgo necessary, lifesaving medical imaging and continue to discuss the benefits and risks of these exams with their healthcare providers.”

For the study, lead author Rebecca Smith-Bindman, MD, and colleagues used a multicenter sample of CT exams from the University of California, San Francisco, International CT Dose Registry. They then forecasted the number of future lifetime cancers in the U.S. population associated with CT imaging delivered in 2023. This resulted in an estimated 62 million patients who underwent 93 million exams that year. 

Smith-Bindman, a UCSF radiologist, and co-authors projected these scans would result in about 103,000 future cancers. Though per-exam risk was higher among children, greater CT use for adults accounted for most projected cases, the authors reported. The most common forecasted types of disease included cancers of the lung (22,400 cases), colon (8,700), leukemia (7,900) and bladder (7,100). Abdominal and pelvic CT, meanwhile, was the main driver, accounting for 37% of forecasted cases (37,500) and 32% of all CT exams (30 million). 

In a corresponding editor’s note, JAMA experts said there is “no simple solution” to the problems posed by the study. However, as one possibility, providers could use artificial intelligence to reduce unnecessary imaging. They also could try alternative modalities that do not use ionizing radiation, reduce CT dosages, and educate clinicians about ways to curb low-value imaging. 

“Although there is some uncertainty around these estimates, the findings suggest that CT scans are likely an important cause of cancer in the United States and could be responsible for as many as 5% of incident cancers annually,” JAMA Internal Medicine Deputy Editor Mitchell H. Katz, MD, and Editorial Fellow Ilana B. Richman, MD, MHS, wrote Monday. “These estimates put CT scanning on par with other well-known risk factors for cancer, including alcohol and obesity.” 

ACR, however, emphasized that imaging exams such as CT are a primary factor in declining cancer death rates, and they’re directly linked to decreased hospital mortality and greater life expectancy. Plus, they help to reduce invasive surgeries, unnecessary admissions and hospital lengths of stay. 

The college urged patients to keep a record of their imaging procedures and speak with their physicians or other medical provider about the risks and benefits of CT imaging.

“ACR will continue to work with decision-makers, federal and state agencies, insurers and others to ensure Americans continue to have access to safe, high-quality radiologic care,” the statement concluded.