Answer to Question #11749 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Diagnostic X Ray and CT

The following question was answered by an expert in the appropriate field:

Q

I am a 41-year-old woman. When I was about 23, I was hospitalized due to a possible pulmonary embolus. It turned out to be pleuritis instead. The doctors did a computed tomography (CT) angiography on my chest. I was at no point given a choice or told about any risks, and they did the CT scan even though my arterial blood values showed no sign of an embolus.

Now my cousin, a 42-year-old super-healthy woman who has never smoked, has been diagnosed with stage IV lung cancer. This awakened my worry regarding that CT scan I had years ago. I have read many studies and articles about this, and I am now in such despair. I have two girls, ages five and two, and I am scared to death of leaving their lives prematurely.

I now realize that the chest CT angiography I had delivers the highest dose a medical scan can deliver, far exceeding any radiation recommendations. It clearly says in several of the studies I read that the younger you are when getting chest CT angiography, the higher your risk of getting cancer later, due to the time you have left to live. If you are a woman, you have a higher risk of getting cancer after this type of scan because of breast and lung tissue factors. Cancer risk increases with acute effective radiation doses ranging from 10–50 millisieverts (mSv), and I was scanned repeatedly for 20 minutes. I can only imagine all the DNA damage that was done.

I can't sleep at night. I do not know how to deal with this. Should I get regular cancer checks of my lungs and breasts? I will then expose myself to even more radiation; even though low-dose CT exams of the lungs are a lot better, they will add to my accumulated radiation load. I feel so helpless and in despair. Am I now a person with a high cancer risk?

A

I'm sorry for your despair and for your cousin's diagnosis. Having someone close to you get a devastating diagnosis like that can certainly be shocking. It does, however, show the random nature of cancer. Environmental exposures, genetic predisposition, and lifestyle choices can affect the chances of developing cancer, but we all have a chance of developing cancer in our lifetimes.

Having a chest CT scan will not measurably increase your risk of lung or breast cancer. The American Association of Physicists in Medicine has a position statement on radiation risk which states in part:

"Risks of medical imaging at effective doses below 50 mSv for single procedures or 100 mSv for multiple procedures over short time periods are too low to be detectable and may be nonexistent. Predictions of hypothetical cancer incidence and deaths in patient populations exposed to such low doses are highly speculative and should be discouraged. These predictions are harmful because they lead to sensationalistic articles in the public media that cause some patients and parents to refuse medical imaging procedures, placing them at substantial risk by not receiving the clinical benefits of the prescribed procedures."

The Health Physics Society also has a position statement on putting radiation risk in perspective which states in part:

"Substantial and convincing scientific data show evidence of health effects following high-dose exposures (many multiples of natural background). However, below levels of about 100 mSv above background from all sources combined, the observed radiation effects in people are not statistically different from zero."

The risks of health effects from radiation doses received during diagnostic imaging procedures are either too small to be observed or are nonexistent. The benefits from properly performed, clinically indicated, diagnostic-imaging procedures, including CT scans, far outweigh any hypothetical cancer risk. Diagnostic medical-imaging procedures provide a medical benefit to you (even if they do not appear to reveal anything) and are of less risk than their alternatives, such as exploratory surgery.

Even if the result of the imaging exam was negative, the physicians were provided information they could use to determine the next course of action. Refusing medical-imaging procedures may result in real and substantial risk by not receiving the clinical benefits of the procedures.

As far as increased cancer screenings, the CT scan you received years ago should not factor into the decision.

Kent Lambert, CHP

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 4 November 2016. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.