Recent research has put the figure of new cancer cases caused by CT (computed tomography) in the United States at around 103,000, in 2023. Out of these, 93,000 are estimated to be adults and 9,700 children. For adults, the most common cancers caused by CT radiation exposure are lung cancer, colon cancer, and leukemia, while in children, the most common are thyroid cancer and lung cancer. It has made the questions about the safety of CT imaging and how to interpret these findings become very prominent.
Can CT Scans Cause 100,000 New Cancer Cases?
CT scans utilize X-rays to generate detailed cross-sectional pictures of the body, thus helping doctors to detect internal injuries and diseases fast and accurately. Unfortunately, since CT involves the use of ionizing radiation, the patient is exposed to a potential cancer risk from that radiation. Scientists gathered data for a wide variety of CT scans, such as the kind of the scan, how often it was done, and the patient’s age. Then, they used radiation-induced cancer models to estimate cancer risks.
One of the most important aspects of their research is the demonstration of a dose-response relationship, in which a higher radiation dose results to a greater risk for cancer. Even though children have a higher risk of developing cancer as a result of radiation due to their still growing bodies, adults are exposed to more radiation than children because they undergo a higher number of scans. According to the researchers, if the present consumption of CT and radiation doses remains constant, the risk of cancer from CT could become as high as that from other well-known risk factors like alcohol or obesity.
How Much Radiation Does a CT Scan Deliver?
The amount of radiation from CT scan is heavily influenced by the area of the body that is being scanned and the type of the equipment that is being used. Generally:
- Head CT: close to 2 millisieverts (mSv)
- Chest CT: around 7 mSv
- Abdominal CT: near 10 mSv
To help the reader comprehend these numbers, the average yearly radiation exposure from natural sources is around 2.4 mSv. That is why, one CT scan, particularly that of the chest or the abdomen, leads to a radiation dose that is many times higher than the normal environmental one.
Children are particularly sensitive to radiation; their cells divide rapidly, making DNA damage and subsequent cancer risk more likely. Studies confirm children undergoing CT scans have a notably higher chance of developing thyroid and lung cancers later on. Adults, particularly those aged 50 to 59, also face increased cancer risk due to both naturally higher baseline risks and cumulative radiation exposure from multiple CT scans.
The International Commission on Radiation Protection (ICRP) maintains that doses accumulated below 100 mSv do not have enough evidence to be directly associated with an increased risk of cancer. However, according to the LNT (linear no-threshold) model that supports the idea of risk even at low doses, which the ICRP also adopts, caution should be exercised. The World Health Organization believes that cancer risk increases significantly after a cumulative exposure of more than 100 mSv of ionizing radiation.
When Is a CT Scan Necessary?
Despite the concern over radiation, CT scans are still indispensable for diagnosis and treatment in a large number of clinical cases. They represent a very valuable tool in the case of severe trauma—in the case of the head, chest, or abdominal injuries—since they provide the necessary information quickly and accurately, thus allowing the correct and timely intervention. In addition, CT is the method of choice in the case of acute cerebrovascular events such as strokes, as it facilitates the identification of hemorrhages and infarctions to direct the treatment.
Hence, CT is the perfect diagnostic tool to locate cancer tumors, to grade the extent of the cancer, and to check the treatment response. However, for minor injuries such as abrasions or sprains, or chronic conditions like gastritis or bronchitis, CT scans should generally not be performed unless the symptoms get worse or new issues appear.
Doctors should think of the benefits and risks before giving the order for a CT scan and patients and their relatives must take part in the decision-making process so that the examination can be done only when really necessary.
Conclusion
CT scans, albeit being very efficient in their role, have an inherent risk of radiation which can lead to cancer, particularly if used frequently or in high doses. Knowing how to balance the need for medically required imaging with the avoidance of unnecessary exposure is of utmost importance in safeguarding the patient. Always talk through your worries and the available options with your doctor to be able to make the right decisions on imaging.
Naresh Trehan is an Indian cardiovascular and cardiothoracic surgeon. After graduating from King George’s Medical University, Lucknow, India, he went on to practice at New York University Medical Center, Manhattan, USA from 1971 to 1988. He returned to India and started Escorts Heart Institute and Research Centre.
