| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Memorial Sloan-Kettering Cancer Center New York, NY 10021
I read with dismay the article by Brenner et al. [1] in the February issue. The claim that using CT in the pediatric population results in an increased risk of cancer is unfounded. Their claim is based on the use of "relative risk models" that have never been proven. Moreover, their calculations are based on a setting of 404 mAs for abdominal CT, much more than is now used for adult CT scanning. This figure was taken from a 1989 survey of CT practice in Britain and does not reflect settings that are used in the United States today. This spurious claim of increased cancer risk has been trumpeted by the media and has resulted in considerable unwarranted anxiety among the parents of our patients.
Certainly, as emphasized in the articles by Paterson et al. [2] and Donnelly et al. [3] in the same issue, we should all use the minimum exposure necessary to obtain a diagnostic examination. This is a good reason for children's imaging to be done by pediatric radiologists.
References
College of Physicians and Surgeons of Columbia University New York Presbyterian Hospital New York, NY 10032
As our article [1] points out, it is important to emphasize that, from a radiation perspective, pediatric CT is very different from adult CT or, indeed, any other radiologic examination. The doses to the organs are much greater than for adults [2], children are much more sensitive to radiation-induced cancer than adults [3], and pediatric CT usage is increasing rapidly, mostly in children who have many years of life in front of them [4].
Perhaps the most important point is that the cancer risks associated with pediatric CT, small though they are (in the approximate range from 1 in 1000 to 1 in 10,000, depending on age and exposure setting), are not hypothetical in the sense of being based on "models" or extrapolations. In fact, they are based directly on measured excess radiation-related cancer rates in individuals (atomic bomb survivors), including children, who were exposed to the same range of organ doses as are children who undergo a CT examination.
The organ dose range of relevance for pediatric CT examinations, assuming a range of mAs settings from 60 to 200 mAs [5, 6], and factoring in the frequency of multiple CT examinations [7], is about 5-100 mSv. The numbers of cancers in atomic bomb survivors exposed to this same low-dose range of relevance to pediatric CT (5-100 mSv) are shown in Table 1. In this low-dose range, a statistically significant radiation-related excess of cancers is observed, both for cancer incidence [8] and for cancer mortality [3]; no extrapolation or use of models is needed. Even at the low-dose (5-20 mSv) end of this low-dose region, a significant increase in radiation-related risk exists (Fig. 1). One might also note that the results shown in this figure are for all ages at exposure, and therefore they are underestimates of the risks in children.
|
|
In summary, radiation-related cancer risks at the same doses that are appropriate to pediatric CT have been directly measured in a human population. The measured risks are small but are statistically significant. Consequently, it would be hard to defend to the public a position that the risks are speculative or unfounded. That position might have been defensible two decades ago, when the atomic bomb survivor data were less mature, but not today.
Of course, it is too early to directly measure the lifetime effects of pediatric CT examinations. The rapid increase in CT use has occurred only over the past decade, whereas the atomic bomb survivor data indicate that the latency period between low-dose exposure and the appearance of a radiation-induced cancer can be 40 years or more. However, a recent case-control study [9] was done of leukemia incidence (for which the time between exposure and disease is typically only a few years) after any pediatric radiological examination (of which CT constitutes 40-67% of the effective dose [7, 10]). A significantly enhanced leukemia risk was associated with two or more pediatric examinations [9].
Thus, strong direct evidence indicates that radiation risks from pediatric CT examinations, though small are real. From an individual standpoint, as we have emphasized [1], the benefits of a CT examination far outweigh this risk. From a public health perspective, however, this small individual cancer risk must be multiplied by a large (and increasing) population of children undergoing CT examination. In our article [1], we assumed that 4% of all CT examinations were performed on children; a very recent survey in the United States [7] suggests that this number is now around 11%—corresponding to about 2.7 million pediatric CT examinations per year. Even a very small individual radiation risk, when multiplied by such a large (and increasing) number of children, is likely to produce a significant long-term public health concern.
It has been 15 years since the first article on pediatric CT dose reduction was published [11], and most pediatric CT examinations are still being performed with adult mAs settings [6]. We hope that the current discussions will contribute toward a significant reduction in the collective dose from pediatric CT examinations, both through the more widespread application of appropriately reduced mAs settings and through a somewhat more selective use of pediatric CT, particularly for flank pain, appendicitis, and blunt trauma [4]. The overwhelming weight of evidence is that the long-term public health benefit would be significant.
References
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
