Scans en ook foto's
bij de tandarts veroorzaken honderden nieuwe gevallen van kanker
per jaar alleen al in Engeland en duizenden doden door kanker
wereldwijd aldus studie aan universiteit van Oxfort
d.d. 2 februari 2004:
Onderzoekers aan de universiteit van Oxford (en gepubliceerd in The Lancet vol 363, p 345) beweren dat bestraling door scans en ook foto's gemaakt bij de tandarts de oorzaak is van 700 nieuwe kankerpatiënten elk jaar alleen al in Engeland. En dan bleek Engeland nog 1 van de landen waar dit percentage laag lag. In Japan zou 30 van de 1000 kankergevallen veroorzaakt worden door het effect van bestraling via foto's en scan's. (3 %) Wereldwijd zou het effect van bestralen duizenden nieuwe gevallen van kanker veroorzaken. Oncologen en deskundigen relativeren dit bericht door te stellen dat door scan's en foto's ook veel kanker vroeg genoeg wordt opgespoord om nog met succes behandeld te kunnen worden en weegt volgens deze deskundigen zwaarder dan het risico op het krijgen van kanker door bestraling. Wel opvallend dat deze deskundigen de uitkomst van deze studie niet tegenspreken. Voorzichtig zijn met het maken van vele scans enz. lijkt dus geboden en u kunt ook zelf de bijwerkingen verminderen en risico op nieuwe kanker verkleinen door bepaalde voeding en bepaalde extra voedingssuppletie, o.a. probiotica. Lees deze pagina: bestraling en voeding met aantal tips geschreven door natuurarts Johan Bolhuis.
Hier het abstract van de studie uit Oxford zoals gepubliceerd in de Lancet d.d. 31 januari 2004 (vol 363, p. 345) (op de website van The Lancet is het volledige rapport te lezen inclusief tabellen enz.) :
Risk of cancer from diagnostic X-rays: estimates for the UK and 14 other countries
Amy Berrington de González, Sarah Darby
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Cancer Research UK Epidemiology Unit (A Berrington de González DPhil) and Clinical Trial Service Unit and Epidemiological Studies Unit (Prof S Darby PhD), University of Oxford, Radcliffe Infirmary, Oxford, UK
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Correspondence to: Dr Amy Berrington de González, Cancer Research UK Epidemiology Unit, University of Oxford, Gibson Building, Radcliffe Infirmary, Oxford OX2 6HE, UK
(e-mail: amy.berrington@cancer.org.uk
)
Summary
Background Diagnostic X-rays are the largest man-made source of radiation exposure to the general population, contributing about 14% of the total annual exposure worldwide from all sources. Although diagnostic X-rays provide great benefits, that their use involves some small risk of developing cancer is generally accepted. Our aim was to estimate the extent of this risk on the basis of the annual number of diagnostic X-rays undertaken in the UK and in 14 other developed countries.
Methods We combined data on the frequency of diagnostic X-ray use, estimated radiation doses from X-rays to individual body organs, and risk models, based mainly on the Japanese atomic bomb survivors, with population-based cancer incidence rates and mortality rates for all causes of death, using life table methods.
Findings Our results indicate that in the UK about 0·6% of the cumulative risk of cancer to age 75 years could be attributable to diagnostic X-rays. This percentage is equivalent to about 700 cases of cancer per year. In 13 other developed countries, estimates of the attributable risk ranged from 0·6% to 1·8%, whereas in Japan, which had the highest estimated annual exposure frequency in the world, it was more than 3%.
Interpretation We provide detailed estimates of the cancer risk from diagnostic X-rays. The calculations involved a number of assumptions and so are inevitably subject to considerable uncertainty. The possibility that we have overestimated the risks cannot be ruled out, but that we have underestimated them substantially seems unlikely.
Lancet 2004; 363: 345-51
Commentaar op studie over risico van bestraling (X-rays) zoals bljkt uit studie van onderzoekers aan de universiteit van Oxford
Twee Duitse Radiologen geven in een artikel in the Lancet commentaar op studie zoals gepubliceerd in The Lancet d.d. 31 januari 2004: vol. 363 p. 345:
Commentary
Risk of cancer from diagnostic X-rays
The role of diagnostic X-rays has evolved from classic conventional radiography and uniform thickslice CT to highly specialised imaging, which has the potential to reduce the overall radiation exposure of individuals undergoing the examination and has better diagnostic accuracy. However, there is no threshold of radiation dose under which the absence of any cancer risk is proven.1 On the other hand, there are no reliable data proving that radiation doses as used in diagnostic X-rays do induce cancer.2
In today's Lancet, Amy Berrington de González and Sarah Darby use cancer-rate data from survivors of the Japanese atomic bombings as a model to study the risk of cancer from diagnostic X-rays. These researchers compiled their data on the incidence of cancers from tumour registers in the UK and 14 other countries. They compared these cancer rates with the numbers of X-ray procedures done in these countries and statistically analysed the number of cancers induced by the radiation exposure from these procedures. The lifetime risk of developing cancer attributable to diagnostic X-rays was 0·6-1·8% in the countries investigated, except in Japan, where the lifetime risk was 3·2%. In the UK, for example, this exposure causes an annual excess risk of 700 cancer cases.
The Japanese survival data are the best available because there are no other data showing the effect of ionising radiation on a large human population; but the data have limitations. One limitation is that the survivors were not only directly exposed with rays from the bomb detonations but also with ßradiation, and, most importantly, by incorporation of radionuclides emitting ßand high-energy radiation from contaminated food, water, and dust in the air. This additional exposure will not occur in patients undergoing radiological examinations but contributes to the morbidity and mortality of the atomic bomb survivors. Additionally the rays to which the atomic bomb survivors were exposed were of a different energy spectrum from that used for diagnostic X-ray. Without better data, however, it is probably adequate to use the Japanese data. But these additional concerns should be taken seriously and the derived numbers for the incidence of cancer caused by X-rays should be critically assessed in future investigations, because the cancer risk is probably overestimated with use of the Japanese data.
The Japanese data were collected between 1991 and 1996. In recent years, at least in Germany and the USA, the number of CT examinations has steadily increased by up to 30% a year while conventional radiography has decreased.3 CT generally leads to a higher exposure with X rays than conventional radiographs of the same section of the body, although the exposure is more dependent on the scanner and exposure parameters than with conventional X rays.4,5 The possible increase of radiation exposure by more extensive use of CT awaits study.
There are differences between countries in how CT parameters are set.3,6 In the USA, exposure parameters are generally set to achieve much higher doses (to reduce image noise) than in Europe, where there is a higher emphasis on reducing the radiation exposure of patients. In some countries, governmental authorities control the radiological exposure of patients and restrict the radiation doses for each kind of examination.7
Strategies and techniques to reduce radiation dose during CT, such as real-time dose-modulation,8-11 are effective but not used in every country in the same way.12 These special techniques are usually only used in newer generations of scanners, which are mostly installed in richer countries.
The upcoming widespread use of digital and digital luminescence (flat panel) radiography means that patients undergoing conventional radiography will be exposed to substantially less radiation.13 Digital radiography with post-processing reduces the number of repeat exposures required because of over-exposure or overblending.
Berrington de González and Darby did not assess the indications or benefits achieved for patients in X-ray examinations. Benefits include the earlier detection of cancers by radiological examinations and the possibility of early treatment, which probably allows more cure of cancers than radiological exposure is able to cause.
A general goal must be to avoid unnecessary X-ray procedures. Up to 30% of chest X-rays may not be indicated;14 unnecessary CT examinations can lengthen hospital stay15 as well as causing radiation exposure. In everyday practice, those ordering radiological procedures should think carefully about the benefit for and the risk to their patients for each examination.
We have no conflict of interest to declare.
*Peter Herzog, Christina T Rieger
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Institute of Clinical Radiology (PH) and Department of Internal Medicine III, Hemato-Oncology (CTR), Ludwig-Maximilians-University Munich, D-81377 Munich, Germany
(e-mail: mail@pherzog.com )
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