CT-associated cancer risk is worryingly high: Are there orthodontic implications?

There is no doubt that for very complex orthodontic cases, CBCT imaging is useful. However, there is a tendency to use CBCT for much more routine orthodontic problems.  I have posted about the risks of this before.  Here is another study suggesting there is a considerable risk of cancer following CT imaging.

In my previous posts, I have emphasised research conducted by investigators using large-scale registries.  These have shown that following head CT scans in children, there is an increased risk of brain cancer. In another study, there was an elevated risk of blood cancer.

In this new study, the team used registry information to illustrate an increasing risk of cancer following CT scans.

A team from San Francisco did this research. Journal of the American Medical Association: Internal Medicine published the paper.

What did they ask?

They asked this question

“How many future cancers could result from radiation exposure from annual CT examinations in the USA?”

What did they do?

This study was a comprehensive analysis of available data. The researchers developed a risk model using patient-level data derived from established registries. The primary data source was the UCSF International CT Dose Registry, which includes CT examinations from 143 US hospitals across 20 states.  

They collected the following data

• CT utilisation from a national survey of 235 hospitals an 78 imaging facilities.
• Then, they identified the distribution of the CT examinations according to body region and clinical indications.
• Next, they estimated absorbed radiation dosages and calculated the mean organ doses in milliGray.
• Finally, they projected future lifetime radiation induced cancer risk using the National Cancer Institutes Radiation Risk Assessment tool.

What did they find?

They provided a significant amount of data for patients of all ages.  I will concentrate on the data for individuals under 18.  However, their overall headline finding was quite concerning.  This was:

In 2023, 93 million CT examinations were performed on 62 million patients. These are projected to lead to 103,000 future cancers. Cancers associated with CT scans could eventually represent 5% of all new cancer diagnoses each year.

We just need to pause to consider this important finding.

Now, let’s look at the data for children who underwent head and neck CT scans.  These are the relevant findings for orthodontic child patients.

• The most frequent projected cancers in children were thyroid and lung.
• Projected risks were greater in children who underwent CT scans when they were less than 1 year old. However, this risk decreased with age. For example, the risk was 2 per 1000 in girls aged 15-17.
• When they looked at projected cancers by CT category, they found that head CT contributed to the most significant number of cancers (53%) in children.  The projected number of cancers from head CT in children was 51,000 per year.

The authors also noted that the potential harms of CT scans are often overlooked, and even minimal cancer risks can result in a significant number of future cancers due to the extensive use of CT in the USA.

Following publication of this paper the Science Media Centre put together this release that included expert reaction to their methods and findings. It is worth a read.

What did I think?

These findings are concerning as they illustrate a clear link between CT scan use and future cancers. It is challenging to extrapolate these findings accurately regarding the effects of CT on orthodontic patients.  Nevertheless, we cannot ignore them.

We must also remember that the data used in this research did not include images taken outside of hospitals. Consequently, we may conclude that the risks are underestimated.  This is certainly relevant to orthodontic patients.

The paper also leads us to several important recommendations regarding the use of CT. The most crucial one is ensuring that the CT is justified and necessary to avoid unnecessary exposure to radiation. Furthermore, we should employ pediatric-specific protocols to reduce exposure to children. Importantly, we must educate healthcare providers to minimise radiation exposure. This is reflected in guidelines produced by our associations and specialist societies.

The key takeaway from this paper and related comments on the research is straightforward: there is a risk associated with CT imaging. However, this risk is justified if the scan is conducted for valid clinical reasons. Therefore, it is essential to thoroughly evaluate and justify this procedure’s risks and potential benefits..

Do we really need that CBCT?

Some readers may argue that we are already utilizing CBCT (Cone Beam Computed Tomography) effectively and safely. However, I’ve observed that many research projects and case reports employ CBCT images for cases where they are not necessary for diagnosis, especially in straightforward situations. In reality, justifying the use of CBCT for routine orthodontic cases is hard.

Furthermore, I’m far from convinced that we need CBCT to determine the position of tooth roots as part of our orthodontic assessment, to identify transverse problems, to find incidental factors or that it’s all fine because the radiation dose is “low”. It’s important to reflect on whether you would expose a close family member to radiation for a routine screening using CBCT.

Final thoughts

This is yet another paper that highlights the risk of cancer from CT images. While we may argue that orthodontic CBCT has a low dose of radiation, we must remember that any amount of radiation carries a risk to future health. Do we really need to jeopardise our child patients’ long-term health to take that CBCT?