CT examinations in America could result in 103,000 future cancers, which would account for 5% of all new cancer diagnoses, according to a study published in JAMA Internal Medicine.
The study examined a risk model through a multicenter sample of CT exams over a 3 year period from the University of California San Francisco International CT dose registry. The authors of the study estimated over 100,000 cancers would result from 93 million scans performed in 2023 alone.
CT scans do use ionizing radiation, as opposed to other imaging modalities such as MRI and ultrasound which do not. It is also well known that ionizing radiation is a clear risk factor for many cancers including the lung, breast, colon and blood cancers, to name a few.
Despite this, an important consideration about the aforementioned study from UCSF is that the results of the study are based off of statistical models, and not real-life patient outcomes. In fact, there are no published peer-reviewed studies that directly link CT scans to cancer, and no studies have shown a direct cause of cancer from CT scans. In other words, the association between cancers and CT scans poses a theoretical risk that has not been shown in real clinical practice.
Concerns from CT scans and cancer stem from the fact that radiation can damage DNA, which could increase one’s cumulative risk for cancer if many scans are received throughout one’s lifetime. However, the amount of radiation from a single CT scan is extremely low. As an example, consider a CT scan of the abdomen and pelvis, which for the average individual delivers a dose of 10 mSv. This dose would be equivalent to the amount of radiation one would naturally receive from the environment for a span of 3 years. This is an exceedingly small dose, particularly when considering the benefits that CT examinations provide individuals and the public.
CT scans are responsible for saving lives by detecting cancers before they spread to distant parts of the body, they have been shown to reduce the amount of invasive procedures that are performed and they reduce hospital stays for patients that are admitted to the hospital. They are invaluable in diagnosing internal injuries, guiding biopsies and monitoring disease progression. In various emergencies, such as a stroke, CT scans can literally be the difference between life and death.
Furthermore, CT technology has evolved in the last decade. Modern machines have the ability to use lower doses, and many screening studies such as those done for lung cancer use specific low dose techniques to minimize the amount of radiation delivered to the body. As an example, a low dose CT scan of the chest performed for lung cancer screening delivers 1.5 mSv of radiation, roughly equivalent to the amount of radiation anyone would receive in the environment for a total of six months.
The fears over CT scans may be largely overstated. Make no mistake- CT scans absolutely use ionizing radiation and patients and physicians should be cautious when ordering them for diagnoses. If there are alternative imaging modalities that can answer the clinical question without radiation those options should be explored.
It is also my hope that these types of studies published in the medical literature inspire physicians and patients to have honest conversations about the benefits and drawbacks of imaging studies so patients can make the most informed choices about their health.
As the American College of Radiology has stated, “Americans should not forgo necessary, life-saving medical imaging and continue to discuss the benefits and risks of these exams with their healthcare providers.”
