Ask the Doc: Why not CT scans for everyone?

Sep. 04, 2013 @ 10:43 AM

Dear Doc Littleton,

Why don’t we just scan everybody with a CT scan to screen for lung cancer?  Seems like everyone I know who gets diagnosed learns about it too late.  If we just scanned everybody at age 50 or 60, wouldn’t that help?

That’s a good question, and I can understand why it would be an appealing thought.  There are several reasons why this isn’t done — yet.  I suspect there will be a day when this will occur, but there are several factors that will determine who is screened.

(Cost, of course, is one factor that we will leave for the politicians and medical pencil-pushers to debate.  Keep in mind it takes equipment, electricity, trained staff, safety training and radiologist (doctors who read x-rays) to obtain a reliable scan. Someone has to pay those costs.)

CT Scan or “CAT Scan”, short for Computed Tomography, was invented in 1972 by British engineer Godfrey Hounsfield and South Africa-born Allan Cormack.  It is an x-ray machine which encircles a patient like a big donut as the patient is moved back and forth on a table.  A CT scan takes spiral like pictures of the head, chest, abdomen, and pelvis and can also recreate special 3-dimensional pictures of bones in certain cases.  Computerization pieces the x-rays together.

Think of a spiral-sliced ham and you get a fairly close idea of how a CT scan takes spiral pictures of the body.

The National Lung Screening Trial studied screening for lung cancer with CT scans and published the results in 2011 in the New England Journal of Medicine (NEJM, August 2011). The trial showed some reduction in the number of deaths from lung cancer, but was complicated by a very high number of “false positives,” or abnormal scans in patients who did not truly have lung cancer.  

However, in 2013 the researchers went back to this same data that they obtained from the original study (NEJM, July 18, 2013).  They categorized patients according to risks for cancer.  In other words, the higher the risk of lung cancer according to age, sex, race, family history of cancer, amount of smoking, and level of lung disease determined which category a patient was classified.

The new results showed that for the high-risk patients, 161 scans would have to be done to prevent one death.  In the low-risk group, 5,300 scans would have to be done to prevent one death.

The problem of false positives still was large and would mean many people would worry over an abnormal scan before it could be confirmed as non-cancerous.

This is a significant result and may provide the selection method to screen the patients who may be at the highest risk of lung cancer.  The final decision will be made by those who control how money is spent in healthcare and that is rarely the patient and the doctor nowadays.

Nevertheless, if you are worried about lung cancer, the most significant thing to do is stop smoking.  Yes, non-smokers get lung cancer, too, but the vast majority of lung cancer is related to smoking.

Remember a pack a day of cigarettes is around $1,500 a year. Think about how it would feel to have $1,500 stolen every year and it might just be the motivation to stop.  Today.

Questions may be emailed to Dr. Littleton at askdrlittleton@gmail.com.

Eric J. Littleton, M.D. is a Family Physician in Sevierville, TN and is a graduate of Tennessee Technological University and University of Tennessee College of Medicine, Memphis. Topics covered are general in nature and should not be used to change medical treatments and/or plans without first discussing with your physician.