Does CT scan cause cancer?

COMPUTERIZED Tomography (CT) Scans is one of the greatest advances in medicine in the last century which expedites early diagnosis with more precision and accuracy, not readily possible before its introduction.


However, whenever a test involves x-rays, concerns about radiation exposure and the risks it poses are seriously monitored and researched by the medical community. Besides the usual evaluation of the cost-benefit equation, the risk-benefit ratio is likewise evaluated on an on-going basis, no matter how good the test is. All in the name of quality medical care and safety.


Recent alarming studies, published in the Archives of Internal Medicine December 14, 2009, stated that radiation from CT scans “may cause cancer decades later,” estimating “about 29,000 future malignancies would occur in the US because of CT scans done in 2007.”

CT scans are done for the head, chest, heart, blood vessels, abdominal organs, soft tissues and bones, etc. If the strict medical indication for CT scan is followed to the letter, there will be a lot less CT scans done around the globe. Patients’ demand for a CT scan, if without medical justification, should be ignored by the physician, for their own safety.

The radiation a CT scan delivers is equivalent to about 100 to 200 times those of conventional chest X-ray. If your doctor says “we will do 100 to 200 chest X-rays on you today,” you will surely be stunned and question its safety, if not refuse altogether. But
practically everybody accepts (some even insist to have) CT scan without care.

Majority of the predicted CT scan victims of cancer are women and about 33 percent of these cancers are projected to happen to those who were 35 to 54 years of age when they had the CT scan, based on an estimated 72 million CT scans performed in 2007, a triple increase in the number of CT scans since 1993. About 30 percent of CT scans done are deemed unnecessary, not medically justifiable.

“We know that there are great medical benefits to CT scans, but they also involve small risks of cancer because of radiation exposure,” said Amy Berrington de Gonzalez, the lead researcher at the National Cancer Institute in Bethesda, Maryland. “For an individual, the risks are small. So if the scan is clinically justified, then the benefits should outweigh the risks,” she added.

The researcher pointed out that “the overall risk for any individual is small and depends on the type of scan given and a person’s age ... A 70-year-old who has a CT scan of the head would have a 1 in 10,000 chance of developing cancer from the test, while a baby who had a chest CT scan would have a 1 in 200 chance.”

Type of cancers
The prediction is that lung cancer, followed by colon cancer and leukemia, will be the most common radiation-related cancer. Fifty percent of those predicted 29,000 people who may develop cancer from CT scan in 2007 will die, according to the study.

This published research also pointed out that if the use of CT scan remains at its present number or higher, “eventually 29,000 cancers every year could be due to past CT scan use.” This translates to about 2 percent of the 1.4 million cancers diagnosed in the United States annually.

“There’s a risk with anything we do, whether it’s taking antibiotics or crossing the street,” stated Donald Frush, chairman of the American College of Radiology’s Pediatric Imaging Commission and chief of the division of pediatric radiology at Duke Medical Center in Durham, North Carolina. “We can’t lose what the benefits of CT scanning are. The benefits are that CT scans save tens of thousands of lives each year in the U.S. and really helps the medical community diagnose things. CT is one of the most invaluable medical advancements in the last 100 years,” Dr. Frush added.

One unfortunate mistake that has complicated the CT scan issue is that of a wrongly programmed CT scan which apparently has happened at Cedars Sinai Hospital in Los Angeles, where patients undergoing CT scan of the head were reportedly exposed to
excess radiation. This news has directed the spotlight on the risk of radiation from CT scan. In view of this, the U.S. Food and Drug Administration on December 7, 2009 issued interim regulations requiring closer monitoring of CT scans after more than 250 cases of exposure to excess radiation were reported since October this year.

Mammography and breast cancer

On another front, a report from the annual meeting of the Radiological Society of North America “verified that annual mammography screenings may be responsible for causing breast cancer in women predisposed to the disease.”

The study included high-risk women and showed that low-dose mammography radiation “increased these women’s risk of developing breast cancer by 150 percent ...women under 29 who have had at least five mammograms are 2.5 times more likely to develop breast cancer than high-risk women who have never undergone low-dose mammography screenings.”

University Medical Center Groningen in the Netherlands’ epidemiologist Marijke C. Jansen-van der Weide cautions physicians when screening younger women, especially those under age 30. The researcher suggested alternative screening tests like Ultrasounds, MRIs, and heat thermography, where no radiation is involved.

Clearing the air

I realize how much fear and confusion this issue has caused the public. The truth of the matter is even the medical community has been impacted by this. After all, the CT scan has been a very reliable diagnostic tool in the physician’s armamentarium for the benefit of his patients.

The debate on this matter is far from over. More studies are presently being conducted to get a good handle on this problem and determine a solution for it.

In the meantime, one thing is clear: where medically indicated, CT scan, which has saved
hundreds of millions of lives since it was first introduced, is a precious tool in competent hands. Unless a superior and safer substitute comes along, CT scan will be with us for some time in man’s fight against diseases, especially cancer.

As always, I am advising patients to discuss in detail with their attending physicians whatever concerns they may have as far as diagnosis, treatment, prognosis, and other details of their condition are concerned.