By how much does every abdominal computed tomography (CT) scan increase a patient's risk of cancer?

From the Guidelines

The risk of cancer from a single abdominal CT scan is estimated to be approximately 0.05% to 0.1%, or about 1 in 1,000 to 1 in 2,000, as supported by the most recent and highest quality study 1. This small increase in lifetime cancer risk varies based on several factors including the patient's age, sex, the specific scan parameters used, and the radiation dose delivered.

• Younger patients generally face a higher lifetime risk than older patients because they have more years ahead during which cancer could develop.
• The typical abdominal CT scan delivers about 10-20 millisieverts (mSv) of radiation, which is roughly equivalent to 3-7 years of natural background radiation exposure.
• This radiation can potentially damage DNA, which may lead to cancer development years or decades later. However, it's essential to balance this small risk against the immediate diagnostic benefits of the scan.
• When medically necessary, the diagnostic information gained from an abdominal CT scan typically far outweighs the small increased cancer risk, especially for patients with acute conditions or those being evaluated for potentially serious diseases. As noted in the study by the American College of Radiology 1, the use of medical radiation has increased significantly over the past few decades, and while there are currently no data showing that high-dose medical diagnostic studies such as computed tomography and nuclear medicine have actually increased the incidence of cancer, the International Commission on Radiological Protection has reported that CT doses can indeed approach or exceed levels that have been shown to result in an increase in cancer.
• The study also suggests that medical exposure might be responsible for approximately 1% of the cancer in the United States 1. In contrast, a more recent study on screening and surveillance for the early detection of colorectal cancer and adenomatous polyps 1 provides a more specific estimate of the risk, stating that a CTC examination in a 50-year-old individual with an estimated organ dose to the colon of 7 to 13 mSv is estimated to add an additional 0.044% to the lifetime risk of colon cancer.
• This study highlights the importance of considering the risks and benefits of medical imaging and the need for careful consideration of the potential long-term harms associated with radiation dose effects from CT examinations.

From the Research

Abdominal CT Scan and Cancer Risk

• The exact increase in cancer risk from every abdominal CT scan is not explicitly stated in the provided studies.
• However, studies have shown that CT scans do increase the risk of cancer due to ionizing radiation exposure 2, 3, 4, 5.
• A study from 2018 estimated the lifetime attributable cancer risks for young adults undergoing repeated CT scans for acute abdominal pain, but did not provide a specific increase in risk per scan 3.
• Another study from 2015 discussed the risk of cancer associated with CT scans in children, but did not provide a direct correlation to abdominal CT scans in adults 5.
• The studies suggest that the risk of cancer from CT scans is a concern, but the exact increase in risk per scan is not clearly defined 2, 3, 4, 5.
• It is essential to weigh the benefits of CT scans against the potential risks and to use the lowest possible radiation doses to minimize exposure 4, 5.

Radiation Exposure and Cancer Risk

• The radiation exposure from CT scans can vary depending on the type of scan, the patient's age, and the scanner used 3, 4.
• Studies have shown that repeated CT scans can lead to high cumulative radiation exposure, increasing the risk of cancer 3.
• The effective doses (EDs) of radiation from CT scans can range from 14.1 mSv to 436.6 mSv, with an average of 70.1 mSv per person 3.
• The risk of cancer from radiation exposure is a concern, and efforts should be made to reduce population-wide CT scan-associated radiation exposure 4.