Rationale and Objectives
This study summarizes the literature on the detection of cancer among indeterminate extracolonic findings on computed tomographic (CT) colonography in five targeted organs.
Materials and Methods
We searched PubMed for English-language literature published between January 1, 1994, and December 31, 2010. We describe extracolonic findings in the kidney, lung, liver, pancreas, and ovary suspect for malignancy as they are associated with high mortality. For each organ, we calculated the median prevalence, positive predictive value (PPV), and false positive rate of malignancy and a pooled false-positive rate across studies.
Results
Of 91 publications initially identified, 24 were eligible for review. Indeterminate renal masses on CT colonography had 20.5% median PPV and low pooled false positive rate of 1.3% (95% confidence interval 0.6–2.0). In contrast, indeterminate masses of the lung, liver, pancreas, and ovary had low PPV (median values ranged from 0% to 3.8%). Indeterminate masses of the ovary resulted in the highest pooled false-positive rate of 2.2%. Results were similar in studies of both screening and nonscreening populations. We estimated the probability of false positive results through the detection of significant extracolonic findings as 46 per 1000 for men and 68 per 1000 for women.
Conclusions
Indeterminate renal masses newly detected on CT colonography have an estimated one in five chance of malignancy and therefore warrant further follow-up to provide a definitive diagnosis. Conversely, indeterminate masses of the lung, liver, pancreas, and ovary are associated with high false positive rates and merit more conservative clinical follow-up.
Computed tomographic (CT) colonography was first described as a method to assess colon neoplasia in 1994 . CT colonography involves insufflation of the colon and rectum with gas and the acquisition of thin-section CT images to visualize polyps and masses using both two-dimensional and three-dimensional interpretation . Multiple studies have demonstrated that the accuracy of CT colonography is similar to that of traditional (optical) colonoscopy for the detection of adenomas and colorectal cancer (ie, sensitivity of 91.3% and specificity of 93.1% for lesions >5 mm) . Both of these screening techniques require cathartic bowel preparation, which is a major deterrent to colorectal cancer screening for patients. However, because CT colonography does not require sedation, it has the potential to increase overall adherence to colorectal cancer screening and is associated with fewer risks than optical colonoscopy.
Unlike traditional colonoscopy, CT colonography can identify extracolonic findings (ie, outside the colon or rectal lumen) because the lung bases, abdomen, and pelvis are included in the examination. To guide management of extracolonic findings, the Working Group on Virtual Colonoscopy developed a rating of extracolonic findings using a scale of E1 to E4 . Under this system, E3 and E4 findings are potentially significant to the patient’s health but incompletely characterized on CT colonography and usually require further imaging and medical follow-up for definitive characterization. E3 findings (eg, pulmonary nodules <1 cm or cystic renal or adnexal masses) are likely insignificant and might require nonurgent follow-up. E4 findings (eg, solid renal masses or pulmonary nodules >1 cm) are likely significant and require urgent follow-up.
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Materials and methods
Literature Review
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Targeted Extracolonic Findings
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Statistical Analysis
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Results
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Table 1
Summary of Reviewed Published Literature of CT Colonography by Calculation of Median Test Properties ∗ Across Five Target Organ Sites, Stratified by Screening and Nonscreening Populations, through 2010
Target Organ No. of Studies FPR (/100) Prevalence (/1000) PPV (/100) Kidneys Screening 6 1.0 0.6 1.5 Nonscreening 13 1.0 4.2 25.0 Mixed/unknown 3 † † † Overall 22 1.1 2.2 20.5 Lung Screening 6 0.2 0.1 20.0 Nonscreening 6 0.7 0.7 0 Mixed/unknown 3 † † † Overall 15 0.7 0.1 3.8 Liver Screening 4 0 1.2 0 Nonscreening 8 1.8 0 0 Mixed/unknown 2 † † † Overall 14 1.3 0 0 Pancreas Screening 2 0.1 0 0 Nonscreening 5 1.4 1.2 25.0 Mixed/unknown 1 † † † Overall 8 0.5 0.5 0 Ovary Screening 5 1.5 0 0 Nonscreening 9 3.7 0 10.0 Mixed/unknown 1 † † † Overall 15 2.5 0 0
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Table 2
Description of Reviewed Published Articles Reporting Extracolonic Findings for Renal Cancer
First Author (Reference) Year Country Sample Size Age Range, y Mean/Median Age. y Men No. of ECFs No. of True Positives FPR (/100) Prevalence (/1000) PPV (/100) Screening populations Ginnerup Pederson B ∗ 2003 Denmark 75 33–78 61 53.3 1 0 1.3 0 0 Gluecker TM 2003 United States 681 41–80 64 62.6 34 1 4.9 1.5 2.9 Chin M ∗ 2005 Australia 432 50–69 † 53.2 6 1 1.2 2.3 16.7 Kimberly JR 2008 United States 143 44–83 57 48 1 0 0.7 0 0 Pickhardt PJ 2010 United States 10,286 † 59.8 52.3 NA 11 † 1.1 † Veerappan GR 2010 United States 2277 † 59 56 16 3 0.6 0.1 18.8 Nonscreening populations Edwards JT 2001 Australia 100 65 47 1 NA † † † Hellstrom M 2004 Sweden 111 19–86 66 59.0 4 1 2.7 9.0 25.0 Pilch-Kowalczyk J 2004 Poland 71 20–85 † 40.8 NA 1 † 14.1 † Rajapaksa RC 2004 United States 250 † 62.5 98 1 1 0 0.4 100 Serracino-Inglott F ∗ 2004 United Kingdom 103 43–88 68 45.6 1 0 1.0 0 † Spreng A 2005 Switzerland 102 20–91 66 61.7 NA 1 † 9.8 † Yee J 2005 United States 500 30–90 62.5 100 8 2 1.2 4.0 25.0 Tolan D 2007 United Kingdom 400 70–96 79.6 37.5 4 2 0.5 5.0 50.0 Khan KY ∗ 2007 United Kingdom 225 62–81 74 40.4 3 0 1.3 0 0 Flicker MS 2008 United States 376 26–89 61 36.7 2 2 0 5.3 100.0 Roberts-Thomson IC 2008 Australia 225 25–85 60 51.0 1 1 0 4.4 100.0 Yucel C 2008 United States 42 60–87 71 38.0 4 NA † † † White TJ 2009 United States 150 40–83 60.9 48.7 NA 3 † 2.0 † Mixed/unknown Hara AK 2000 United States 264 33–88 64 55.3 9 2 2.7 7.6 22.2 Iafrate F 2008 Italy 136 70–92 81 NA 1 NA † † † Park SK 2009 South Korea 920 34–87 57.3 58.1 3 NA † † †
ECF, extracolonic finding; NA, not available; CI, confidence interval.
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Table 3
Description of Reviewed Published Articles Reporting Extracolonic Findings for Lung Cancer
First Author (Reference) Year Country Sample Size Age Range, y Mean/Median Age, y Men No. of ECFs No. of True Positives FPR (/100) Prevalence (/1000) PPV (/100) Screening populations Ginnerup Pederson B 2003 Denmark 75 33–78 61 53.3 1 1 0 1.3 100.0 Gluecker TM 2003 United States 681 41–80 64 62.6 26 1 3.7 0.1 3.8 Chin M 2005 Australia 432 50–69 † 53.2 3 0 0.7 0 0 Kimberly JR 2008 United States 143 44–83 57 48 23 NA † † † Pickhardt PJ 2010 United States 10,286 † 59.8 52.3 NA 8 † 0.1 † Veerappan GR ∗ 2010 United States 2277 † 59 56 5 1 0.2 0.0 20.0 Nonscreening populations Rajapaksa RC 2004 United States 250 † 62.5 98 3 NA † † † Spreng A 2005 Switzerland 102 20–91 66 61.7 NA 1 † 1.0 † Yee J 2005 United States 500 30–90 62.5 100 7 0 1.4 0.0 0.0 Tolan D 2007 United Kingdom 400 70–96 79.6 37.5 7 6 0.3 1.5 85.7 Roberts-Thomson IC 2008 Australia 225 25–85 60 51.0 2 NA † † † White TJ 2009 United States 150 40–83 60.9 48.7 NA 1 † 0.7 † Unknown/mixed Hara AK 2000 United States 264 33–88 64 55.3 8 0 3.0 0.0 0 Iafrate F 2008 Italy 136 70–92 81 NA 1 NA † † † Park SK 2009 South Korea 920 34–87 57.3 58.1 9 NA † † †
ECF, extracolonic finding; NA, not available.
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Table 4
Description of Reviewed Published Articles Reporting Extracolonic Findings for Ovarian Cancer
First Author (Reference) Year Country Sample Size Age Range, y Mean/Median Age, y No. of ECFs No. of True Positives FPR (/100) Prevalence (/1000) PPV (/100) Screening populations Ginnerup Pederson B 2003 Denmark 35 33–78 61 1 0 2.9 0 0 Gluecker TM 2003 United States 255 41–80 64 6 0 2.4 0 0 Chin M 2005 Australia 202 50–69 3 0 1.5 0 0 Pickhardt PJ 2008 United States 1199 40–90 58 13 0 1.1 0 0 Veerappan GR 2010 United States 1002 59 5 0 0.5 0 0 Nonscreening populations Morrin MM 1999 United States 28 22–96 1 NA ∗ ∗ ∗ Edwards JT 2001 Australia 53 65 3 0 5.7 0 0 Serracino-Inglott F 2004 United Kingdom 56 43–88 68 5 1 7.3 17.9 20.0 Spreng A 2005 Switzerland 39 20–91 66 3 1 5.3 25.6 33.3 Khan KY 2007 United Kingdom 134 62–81 74 5 0 3.7 0 0 Tolan D 2007 United Kingdom 250 70–96 79.6 5 0 2.0 0 0 Flicker MS 2008 United States 238 26–89 61 3 1 0.8 4.2 33.3 Roberts-Thomson IC 2008 Australia 110 25–85 60 3 0 2.7 0 0 Yucel C 2008 United States 26 60–87 71 1 NA ∗ ∗ ∗ Unknown/mixed Park SK 2009 South Korea 385 34–87 57.3 1 NA ∗ ∗ ∗
ECF, extracolonic finding; NA, not available; CI, confidence interval.
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Discussion
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