Analysis: Does CT raise cancer risk?

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.