Rationale and Objectives
The aim of this study was to analyze the morphologic and functional features of metastatic lymph nodes of colorectal carcinoma on 18 F-fluorodeoxyglucose positron emission tomographic (PET)/computed tomographic (CT) images and correlate these with pathologic results to explore the best diagnostic performance.
Methods
Sixty-eight patients without any previous treatment underwent 18 F-fluorodeoxyglucose PET/CT examinations and subsequent operations. All lymph nodes were evaluated by recording short diameter and maximum standardized uptake value (SUVmax) on axial images and were carefully verified on the surgically resected specimens. The radiologic diagnostic efficacies on the basis of different diagnostic criteria were compared and evaluated with pathologic results.
Results
There was a significant difference for SUVmax between metastatic and benign juxtaintestinal lymph nodes ( F = 96.836, P = .000) and a correlation between size and SUVmax in metastatic juxtaintestinal lymph nodes ( r = 0.352, P = .038). Diagnosing according to short diameter ≥ 10 mm and SUVmax ≥ 2.5, the sensitivity, specificity, positivity prediction value (PPV), and negative prediction value (NPV) were 10.00%, 98.26%, 66.67%, and 75.84% and 82.50%, 90.43%, 75.00%, and 93.69%, respectively. Considered together, the sensitivity, specificity, PPV, and NPV were 10.00%, 99.13%, 80.00%, and 76.00%, respectively. Receiver-operating characteristic curves showed that the best cutoff values for SUVmax and short diameter were 2.0 and 4.85 mm, respectively; the corresponding sensitivity, specificity, PPV, and NPV, were 91.43%, 87.83%, 69.57%, and 97.12% and 85.71%, 60.87%, 40.00%, and 98.2%, respectively. Considered together, the sensitivity, specificity, PPV, and NPV were 95.00%, 86.96%, 71.70%, and 98.04%, respectively.
Conclusions
Fluorine-18-fluorodeoxyglucose uptake was a more reliable indicator in diagnosing malignant juxtaintestinal lymph node of colorectal carcinoma. The optimal diagnostic efficacy could be reached by considering morphologic and functional features together.
A great deal of research has shown that lymphatic metastasis is the most valuable prognostic factor for patients with resectable primary tumors . In addition, the survival rate of patients with colorectal carcinoma after operation would be markedly increased if the number of resected lymph nodes increased. Thus, it has been suggested that no fewer than 12 lymph nodes should be resected during an operation for colorectal carcinoma . Therefore, it is of great significance to precisely assess the range of lymph nodes involved preoperatively and to resect them during the operation to determine the correct nodal staging of colorectal cancer and subsequent therapy.
Computed tomographic (CT) imaging and magnetic resonance imaging (MRI) were once the primary noninvasive methods for preoperative diagnosis of lymphatic metastasis of colorectal carcinoma. The identification of metastatic lymph nodes with CT imaging and MRI was based mainly on the size of lymph nodes, and a short-axis diameter > 1cm was accepted as the diagnostic criterion in many previous studies. However, the limitations of the simple morphologic criteria were obvious; metastases in normal-sized lymph nodes could be missed, and lymph node enlargement could not be reliably differentiated from cancerous infiltration. Thus, the accuracy of the detection of metastatic lymph nodes and nodal staging has been unsatisfactory for many years .
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Materials and methods
Patients and Imaging
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18 F-FDG PET/CT Imaging
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18 F-FDG PET/CT Image Interpretation
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Statistical Analysis
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Results
Correlations of the SUVmax of Primary Tumors with and without Metastatic Lymph Nodes
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Correlation between the Size and SUVmax of Juxtaintestinal Lymph Nodes
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Table 1
Morphologic and Metabolic Characteristics of Juxtaintestinal Lymph Nodes
n SUVmax Short Diameter (mm) Mean ± SD Range Mean ± SD Range Metastatic lymph nodes 40 3.27 ± 1.37 0.78–8.59 7.11 ± 2.45 4–15 Nonmetastatic lymph nodes 115 0.98 ± 1.18 0.00–7.85 4.45 ± 2.25 1–14
SD, standard deviation; SUVmax, maximum standardized uptake value.
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Diagnostic Efficacies for Juxtaintestinal Lymph Nodes
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Table 2
Comparison between Pathologic and PET/CT Results for Short Diameter ≥ 10 mm in Juxtaintestinal Lymph Nodes
PET/CT Imaging Pathology Metastatic Nonmetastatic Total Metastatic 4 2 6 Nonmetastatic 36 113 149 Total 40 115 155
CT, computed tomography; PET, positron emission tomography.
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Table 3
Comparison between Pathologic and PET/CT Results for SUVmax ≥ 2.5 in Juxtaintestinal Lymph Nodes
PET/CT Imaging Pathology Metastatic Nonmetastatic Total Metastatic 33 11 44 Nonmetastatic 7 104 111 Total 40 115 155
CT, computed tomography; PET, positron emission tomography; SUVmax, maximum standardized uptake value.
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Table 4
Comparison between Pathologic and PET/CT Results for SUVmax ≥ 2.0 and Short Diameter ≥ 4.85 mm in Juxtaintestinal Lymph Nodes
PET/CT Imaging Pathology Metastatic Nonmetastatic Total Metastatic 38 15 53 Nonmetastatic 2 100 102 Total 40 115 155
CT, computed tomographic; PET, positron emission tomographic; SUVmax, maximum standardized uptake value.
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Table 5
Comparison between Pathologic and PET/CT Results for SUVmax ≥ 2.5 and Short Diameter ≥ 10 mm in Juxtaintestinal Lymph Nodes
PET/CT Imaging Pathology Metastatic Nonmetastatic Total Metastatic 4 1 5 Nonmetastatic 36 114 150 Total 40 115 155
CT, computed tomographic; PET, positron emission tomographic; SUVmax, maximum standardized uptake value.
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Efficacy of 18 F-FDG PET/CT Imaging for Diagnosing Abdominal Nonjuxtaintestinal Metastatic Lymph Nodes of Colorectal Cancer
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Table 6
Comparison between Pathologic and PET/CT Results in Nonjuxtaintestinal Lymph Nodes
Number Position Short Diameter (mm) SUVmax PET/CT Pathology 1 Root of sigmoid artery 6.8 3.95 1 1 2 Root of ileocolic artery 12.3 0.90 0 0 3 Root of ileocolic artery 5.0 2.50 1 1 4 Root of ileocolic artery 7.0 3.40 1 1 5 Root of mesentery No detection 0 1 6 Left external iliac artery 18.0 5.2 1 1 7 Before sacrum 10.8 3.76 1 1 8 Before sacrum 9.2 3.38 1 0 9 Before sacrum 4.2 3.18 1 0 10 Root of ascending colon artery 6.3 1.2 0 0 11 Root of ascending colon artery 4.2 1.49 0 0 12 Root of ascending colon artery 3.7 1.51 0 0 13 Root of ascending colon artery 4.8 1.89 0 0 14 Left hypogastric 10.9 2.7 1 1 15 Left obturator foramen 10.5 3.88 1 0 16 Left obturator foramen 6.8 1.82 0 0 17 Superior rectal artery 3.0 1.08 0 0
CT, computed tomography; PET, positron emission tomography; SUVmax, maximum standardized uptake value.
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Discussion
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