Table 1.
Risk of Malignancy after CT Scan: Studies with Primary Data for Both Patient Exposure and Outcome.
| Author, Year |
Study Design (sample size) |
Estimated Risk of Subsequent Malignancy Associated with CT |
Counts and Types of Malignancy/ Neoplasm Identified or Predicted |
Method of Risk Calculation |
Age at the Time of CT |
Additional Comments |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mathews, 201331 | Historical cohort study, n = 10,939,680, among which 680,21 1 were exposed to CT |
|
|
Estimated IRRs by Poisson regression | 0–19 years at the start of the study | Electronic Medicare records of Australians 0–19 years old between 1985 and 2005 The cohort was followed through 2007 by electronic linkage to the Australian Cancer Database and the National Death Index |
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| Incidence rate ratiosa for type of cancer
|
Number of malignancies reported in CT-exposed subjects
|
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| B | T | L | A | B | T | L | A | |||||||
|
|
|
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| Brain CT | 2.44 (2.12–2.81) | 1.33 (1.13–1.57) | 1.16 (0.99–1.37) | 1.23 (1.18–1.29) | Brain CT | 210 | 155 | 149 | 1964 | |||||
| Facial bones CT | 1.60 (1.04–2.47) | 1.53 (1.05–2.22) | 1.07 (0.70–1.62) | 1.14 (1.01–1.28) | Facial bones CT | 21 | 28 | 22 | 280 | |||||
| Spine/neck CT | 1.19 (0.69–2.05) | 1.78 (1.24–2.58) | 1.31 (0.85–2.04) | 1.13 (1.00–1.28) | Spine/neck CT | 13 | 29 | 20 | 252 | |||||
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| Pearce, 20125 | Historical cohort study, n = 178,604 for leukemia analysis, n = 176,587 for brain tumor analysis |
|
Leukemia: 74 of 178,604 patients Brain tumors: 1 35 of 176,587 patients |
Poisson relative risk models fitted by maximum likelihood | <22 years | Sites scanned: 64% head, 9% abdomen, 7% chest After 2001,5–10 head CTs in children < 15 yrs result in accumulation of about 50 mGy red bone marrow dose and 2–3 head CTs results in about a 60 mGy cumulative brain dose |
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| Cumulative exposure Relative risk (95% CI) Reference0020b: <5 mGy | ||||||||||||||
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| Leukemia | >30 mGy (mean 51.1 mGy): 3.18(1.46–6.94) | |||||||||||||
| Brain tumors | Estimate 1:50–74 mGy (mean 60.4 mGy): 2.82 (1.33–6.03) Estimate 2: >50 mGy (mean 104.2 mGy): 3.32 (1.84–6.42) |
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Abbreviations: IRR, incidence rate ratios; B, brain; T, thyroid; L, leukemia; A, all cancer.
a
For exposed versus unexposed by site of CT scan and type of cancer, based on a 1-year lag period, stratified for age, sex, and year of birth.
b
The reference category to which the higher exposures were compared was <5 mGy.