June 13, 2012Volume 7 - Issue 24

DynaMed Weekly Update

For the week ending June 8, 2012

Last week 281 articles were evaluated via DynaMed's Systematic Literature Surveillance and 122 were added to DynaMed content.

Based on the editors' criteria of selecting "articles most likely to change clinical practice," one article of significant interest was selected for the DynaMed Weekly Update.

Feature Article

Childhood CT Scans May Slightly Increase Lifetime Risk of Leukemia and Brain Tumors


As previously highlighted in a Dynamed Weekly Update in 2010 (volume 5, issue 2), radiation exposure from computed tomography (CT) scans in adults has been associated with increased lifetime cancer risk (Arch Intern Med 2009 Dec 14;169(22):2071). A new retrospective cohort study has evaluated the risks of leukemia and brain tumors associated with childhood CT scans. Patients in Great Britain who had at least 1 CT scan before the age of 22 years and had no previous cancer diagnosis were assessed for absorbed radiation doses in red bone marrow and brain tissue. A cohort of 178,604 patients was analyzed for incidence of leukemia and a cohort of 176,587 patients was analyzed for brain tumors. Patients were excluded for diagnosis of leukemia within 2 years or brain tumor with 5 years of CT scan to reduce the risk of counting preexisting cancers.


Absorbed radiation dose, measured in milliGrays (mGy) varies with age and scan location. For a 5-year old child receiving a head CT, the typical brain exposure would be about 28 mGy and the estimated red bone marrow dose would be about 9 mGy. A chest CT gives lower doses to both brain tissue and bone marrow. A 15-year old adolescent would typically receive a brain dose of about 44 mGy and a bone marrow dose of 5 mGy from a head CT.


During follow-up of up to 23 years, leukemia was diagnosed in 74 patients (0.04% of cohort) and brain tumors were diagnosed in 135 patients (0.08% of cohort). Increasing radiation dose was associated with increased cancer risk. For each 1 mGy increase in dose the excess relative risk for diagnosis of any leukemia was 0.036 (95% CI 0.005-0.12), and the excess relative risk for any brain tumor was 0.023 (95% CI 0.01-0.049). Compared to cumulative doses < 5 mGy, a cumulative dose of ≥ 30 mGy was associated with increased risk of leukemia (relative risk 3.18, 95% CI 1.46-6.94) and a cumulative dose of 50-74 mGy was associated with increased risk of brain tumor (relative risk 2.82, 95% CI 1.33-6.03).


In terms of absolute risk, these results correspond to an estimate of 1 additional case of leukemia and 1 additional brain tumor over 10 years per 10,000 children having a head CT scan at ≤ 10 years old. Though low, these risks should be considered when weighing the clinical value of a CT scan in a child, especially when other options may exist (Lancet 2012 Jun 7 early online).


For additional information, see the Acute lymphoblastic leukemia (ALL), Myelodysplastic syndrome, and Brain tumor topics in DynaMed.


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About DynaMed Weekly Update

Prepared by the clinician members of the DynaMed Editorial Team, DynaMed Weekly Update is a compilation of one to five articles selected from DynaMed's Systematic Literature Surveillance as articles most likely to change clinical practice.

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CME Information
Physicians: 0.25 AMA PRA Category I Credit(s)™
Family Physicians: 0.25 Prescribed credits
Nurse Practitioners: 0.25 Contact hours
Release Date: June 13, 2012

Expiration Date: June 13, 2013
Estimated Completion Time:

15 minutes

There is no fee for this activity.


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In order to receive your certificate of participation, you should read the information about this activity, including the disclosure statements, review the entire activity, take the post-test, and complete the evaluation form. You may then follow the directions to print your certificate of participation. To begin, click the CME icon at the end of the article.


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Learning Objectives 

Upon successful completion of this educational program, the reader should be able to: 

1. Discuss the significance of this article as it relates to your clinical practice.
2. Be able to apply this knowledge to your patient's diagnosis, treatment and management.


Faculty Information


Alan Ehrlich, MD- Assistant Clinical Professor in Family Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA; Deputy Editor, DynaMed, Ipswich, Massachusetts, USA


Michael Fleming, MD, FAAFP - Assistant Clinical Professor of Family Medicine and Comprehensive Care, LSU Health Science Center School of Medicine, Shreveport, Louisiana, USA; Assistant Clinical Professor of Family Medicine, Department of Family and Community Medicine, Tulane University Medical School, New Orleans, Louisiana, USA; Chief Medical Officer, Amedisys, Inc. & Antidote Education Company


Dr. Ehrlich, Dr. Fleming, DynaMed Editorial Team members, and the staff of Antidote Education Company have disclosed that they have no relevant financial relationships or conflicts of interest with commercial interests related directly or indirectly to this educational activity.


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AAFP: Enduring Material activity, DynaMed Weekly Update, has been reviewed and is acceptable for up to 13 Prescribed credits by the American Academy of Family Physicians. AAFP certification begins March 7, 2012. Term of approval is for one year from this date with the option of yearly renewal. Each Weekly Update is worth .25 Prescribed credits. Physicians should claim only the credit commensurate with the extent of their participation in the activity. 


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