Study quantifies risk of cancer from x-rays

[Guest guest]

Rheumawire

Feb 4, 2004

Study quantifies risk of cancer from x-rays

Oxford, UK - New research suggesting that around 700 of the 124 000

cases of cancer diagnosed in the UK each year are caused by exposure to

medical x-rays may hold special significance for rheumatoid arthritis

(RA) patients and their physicians, as this patient group must undergo

more diagnostic imaging than members of the general population. The

findings are published in the January 31, 2004 issue of the Lancet [1].

Drs Amy Berrington de González (Cancer Research UK Epidemiology Unit,

Oxford, UK) and Darby (University of Oxford, UK) estimated cancer

risk based on the annual number of diagnostic x-rays in the UK and in 14

other developed countries (Australia, Canada, Croatia, Czech Republic,

Finland, Germany, Japan, Kuwait, the Netherlands, Norway, Poland,

Sweden, Switzerland, and the US).

Overall, patients in Japan had the highest risk because they underwent

more diagnostic imaging procedures than people in any of the other

studied countries1477 for every 1000 people. By comparison, German

patients underwent 1254 x-rays annually per 1000 people; patients in the

US underwent 962 x-rays annually per 1000 people, and Australian

patients underwent 565 x-rays annually per 1000 people.

Almost 7600 cancers diagnosed each year in Japanor 3.2% of the total

cancer casesare linked to diagnostic imaging procedures, the study

showed. The researchers estimate that the lifetime risks attributed to

radiation exposure from diagnostic x-rays is roughly 0.6% in the UK,

which translates to roughly 700 of the 124 000 cancer cases identified

in the country each year. In the US, the lifetime risk of cancer caused

by radiation exposure from x-rays is approximately 0.9%almost double the

risk suggested in 1 of the only other studies to examine the issue [2].

This lifetime risk accounts for about 5700 cancers per year in the US.

" The possibility that we have overestimated the risks cannot be ruled

out, but it seems unlikely that we have underestimated them

substantially, " the study authors conclude.

In an accompanying editorial [3], Drs Herzog and T

Rieger (University of Munich, Germany) point out that the researchers

did not assess the potential benefits of diagnostic radiation, including

earlier detection of cancers and the possibility of earlier, more

effective, and less harsh treatment.

In addition, they point out that the new study used cancer-rate

information from Japanese bomb survivors to study the risks of cancer

from diagnostic x-ray exposure, but this population also had different

exposures, including those associated with ingesting contaminated food,

water, and dust.

" This is a very good article and it reminds us as physicians that we

should respect radiation and use diagnostic tests for good reason, not

unnecessarily, " says Dr Jay (Ochsner Clinic Foundation, Baton

Rouge, LA), who reviewed the study for rheumawire.

As to what the increased risk of cancer from diagnostic x-rays would be

for RA patients, " it's impossible to say, " he tells rheumawire. " People

with RA have an increased risk of cancer to begin with, specifically

lymphomas. "

His advice? " I try to tell people that we should use the tests we have,

which are wonderful tests, only when they are clinically indicated. "

For rheumatologists, however, " they have to use these tests to follow

disease progression, but they should try to do it as little as they need

to, " he says.

Mann

Sources

1. Berrington de González A and Darby S. Risk of cancer from diagnostic

x-rays: estimates for the UK and 14 other countries. Lancet 2004;

363:345-351.

3. Herzog, P and Rieger CT. Risk of cancer for diagnostic x-rays. Lancet

2004; 363:304.

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org