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Does CT Raise Cancer Risk?


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http://www.upi.com/Health_Business/Anal ... risk/1594/

BOSTON, July 17 (UPI) -- Patients who receive a cardiac CT scan also receive significant levels of radiation that in some cases may lead to cancer later in life -- and young women are particularly at risk, a new study has found.

The risk of cancer is high enough for young people and women that physicians should be very selective in ordering the common test, called a 64-slice CTCA or computed tomography coronary angiography, said Andrew Einstein, a professor of cardiology at Columbia University.

The study found that of women in their twenties who are given a CTCA test, one out of 143 would go on to develop cancer, probably breast cancer.

`"For every patient, docs need to make a risk-benefit analysis. And ultimately make a decision about what is best for the patient," Einstein told United Press International.

"If a female patient comes in and says their mother died of heart attack at 40 and she has cholesterol through the roof and she smokes, you do what you can and you don't worry about the radiation," Einstein said.

But, "sometimes people want to have CAT scans of their heart to see what it looks like. This is generally not appropriate. There should be a very good reason to get this test, as assessed by the person's doctor," he added.

His study appears in Wednesday's Journal of the American Medical Association.

However, Einstein stressed, "Patients shouldn't be alarmed" about the risks of the test.

Coronary artery disease accounts for one out of five deaths. More than 6 million people per year show up at emergency rooms complaining of chest pain, Einstein said.

The CTCA is heavily used by emergency rooms.

The CTCA detects plaque blockages in coronary arteries and is given to people with known or suspected heart disease, Einstein said. The test involves getting an injection of dye in the arm, then going inside a large tube-like machine that takes the images.

The CTCA will take hundreds of X-rays during one test, Einstein said. It takes 20 minutes to complete the test.

'It provides beautiful pictures of coronary arteries and can be life-saving," Einstein said. The 64-slice CTCA was approved for use in 2004 and is widely used.

The CTCA test exposes the heart, lungs, breasts, thymus, esophagus and other organs to radiation, Einstein said.

According to the study, women were at higher risk, and people who are younger were at higher risk of developing cancer due to exposure to a CTCA test.

The risk decreased with age, mainly because there is less time for cancer to grow before one dies of another cause, Einstein said.

The risk of cancer was quite low in men, especially older men. For 20-year-old men given the CTCA test, 1 out of 686 would be expected to develop lung or other cancer during their life, as a result of the test. For 60-year-old men, about 1 in 1,241 would develop cancer.

And for 80-year old men who receive the test, 1 out of 3,261 would be expected to develop lung cancer during their lifetime.

Women are more sensitive to radiation exposure, so the study took this into consideration. For 40-year old women who take the test, one out of 284 would be expected to develop breast, lung or other cancer as a result of a CTCA scan.

"For a lot of patients, men and older people, this gives us reassurance that despite a perception of high risk, the cancer risk of CTCA is relatively low. That is not the case for younger women," Einstein said.

For unknown reasons, the study found that of women under 32 who developed cancer from the test, the majority would develop breast cancer. For women over 32, lung cancer became the dominant cancer.

In the study, Einstein calculated the risk of overall cancer or cancer of individual organs due to the CTCA by using a standard mathematical model called Monte Carlo simulations.

He plugged in estimates about cancer and radiation exposure put forth by an expert panel of the National Academies of Science, called BEIR VII.

The estimates are based on the cancers that resulted in Japan after the atomic bombs were dropped, and in women given X-rays to treat tuberculosis from the 1920s to 1954.

These data show that it takes a minimum of 12 years after exposure to radiation for cancer to grow, Einstein said.

People generally do not receive more than one CTCA in a lifetime but sometimes this does happen and the risk from the radiation exposure increases, he said.

Other tests are available to detect heart disease, and Einstein suggested that in light of the study results, physicians consider using them with younger women when appropriate.

Another good option is to use a CTCA scanner that offers extra protection against radiation exposure, called an ECTM. These machines are newer and less common but reduce exposure to radiation by 35 percent, Einstein said.

The CTCA machines have been in use since the late 1990s, and from the beginning there has been concern about the radiation they expose patients to, said Ann Bolger, professor of cardiology at the University of California San Francisco and a spokeswoman for the American Heart Association.

"This is a very eye-opening look at this issue," Bolger told UPI. "In women the sensitivity is increased and this is an issue we have to deal with," she said.

However, "no matter who you are radiation exposure is potentially a very dangerous thing. It's very important to save the exposures for those times when it is medically necessary, and can be life saving," Bolger added.

Wilfred Mamuya, a cardiologist at Massachusetts General Hospital, said physicians are very aware of the radiation exposure of the tests, and have made their concerns known to manufacturers.

"I would have a hard time subjecting anyone to radiation who does not have cardiac symptoms," Mamuya told UPI.

Manufacturers are trying to make cardiac imaging devices that emit less radiation, he said.

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