CT scan and cancer risk

Exposure to low-dose radiation from computed tomography (CT) scans may increase risk of certain cancers, seen in a Taiwanese cohort.

Medical imaging tests are powerful diagnostic tools that provide a picture of the body’s interior. In computed tomography (CT), the patient is moved through a scanner as x-ray images are taken in all directions to produce a detailed, cross-sectional view of the body. While CT scans are critical for early and accurate disease diagnosis, they also represent a significant source of ionizing radiation, a known human carcinogen. With rapid increase in the utilization of CT scans over the last two decades, the diagnostic benefits must be weighed against potential patient harms that come from radiation exposure and associated cancer risk.

Researchers from Taipei Medical University studied the effect of adult exposure to low-level ionizing radiation from medical imaging tests on the risk of developing various types of cancer. The results, published in JNCI Cancer Spectrum, found that exposure to medical radiation from CT scans was associated with a significantly increased risk of thyroid cancer and leukemia.

Using population data from the National Health Insurance dataset in Taiwan, the researchers followed 22,853 thyroid cancer, 13,040 leukemia, and 20,157 non-Hodgkin lymphoma cases from 2000 to 2013. Demographic and medical information were collected, including details on disease diagnoses, medical procedures, and drug prescriptions. Patients were excluded if they were under 25 years old at the time of cancer diagnosis, had less than three years of follow-up before cancer diagnosis, or had a history of cancer before the year 2000.

“Our study found that CT scans are associated with an increased risk of thyroid cancer and leukemia in adults in all ages and with non-Hodgkin lymphoma in young adults,” said Yu-Hsuan Joni Shao, lead author of the paper. “The risk is stronger in patients who have higher cumulative doses from multiple scans. The increased numbers of people undergoing CT scans have become a public health issue.”


Written by Cheryl Xia, HBMSc



Shao, Y.-H., Tsai, K., Kim, S., Wu, Y.-J. & Demissie, K. Exposure to Tomographic Scans and Cancer Risks. JNCI Cancer Spectrum pkz072 (2019) doi:10.1093/jncics/pkz072.

Emily Tobin. Radiation from CT scans associated with increased risk for cancer. EurekAlert! (2019).

Image by David Mark from Pixabay

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