Rationale and Objectives
To investigate the relationship between apparent diffusion coefficient (ADC) values and the Ki-67 staining index (Ki-67 SI), a tumor proliferation marker, in prostate cancer (PCa).
Materials and Methods
Forty-three patients with PCa and thirty-six patients with benign prostatic hyperplasia (BPH) underwent diffusion-weighted (DW) imaging on 3T magnetic resonance (MR) with pelvic phased-array coil. The ADC values of PCa were calculated from two DW images ( b = 0, 800 s/mm 2 ). Immunohistochemical staining for Ki-67 was used to determine the Ki-67 SI of PCa and BPH. The Pearson correlation test was used to examine the relationship between ADC values and the Ki-67 SI. The ADC values of PCa with different level of Ki-67 SI were compared using an independent-sample t -test.
Results
The mean (±standard deviation [SD]) Ki-67 SI of PCa (7.23 ± 5.29%) was higher than that of BPH (2.11 ± 1.90%) ( P < .001). The mean (±SD) ADC value (10 −3 mm 2 /s) of PCa (0.850 ± 0.155) was lower than that of BPH (1.173 ± 0.245) ( P < .001). The ADC values of PCa were negatively correlated with the Ki-67 SI ( r = −0.459, P = .002). The mean ADC values of PCa with Ki-67 >3.5% and ≤3.5% were (0.803 ± 0.094) and (0.936 ± 0.208), respectively. The former was significantly lower than the latter ( P = .031). The ADC values of PCa with Ki-67 >7.1% and ≤7.1% were (0.779 ± 0.081) and (0.906 ± 0.178), respectively. The difference was significant ( P = .004).
Conclusion
The ADC values of PCa could reflect the tumor proliferative activity and the differentiated degree of PCa.
Prostate cancer (PCa) is one of the most common malignant tumors in males in America and Europe. The incidence of PCa in China has increased gradually in recent years. PCa has many available treatment alternatives, yet selecting one optimal option is difficult . Knowledge of the tumor aggressiveness before treatment helps doctors predict the prognosis of patients and personalize treatment. Tumor proliferation activity is one of the indicators to evaluate the aggressiveness. Ki-67 is a proliferation-related nuclear antigen and is expressed in all cycling cells except for resting cells in the G0 phase. The Ki-67 staining index (SI) reflects the proliferation activity of tissue. Furthermore, the Ki-67 SI is a marker of tumor progression, treatment outcome, biochemical recurrence, and progression-free survival . The relationship between Ki-67 SI and clinical results, such as Gleason score, prostate-specific antigen (PSA), and stage, has been investigated in previous studies .
Magnetic resonance imaging (MRI), a noninvasive method, has been used in staging , localizing , and assessing the aggressiveness of PCa . The diffusion-weighted (DW) imaging was one of the most important MRI techniques. It evaluates the random Brownian motion property of water molecules in tissue. The apparent diffusion coefficient (ADC) can be calculated from two or more DW images obtained with different b values and can avoid the T2 shine-through effect on DW images. PCa exhibits impeded diffusion compared with surrounding tissue, manifesting with hyperintense on DW images and hypointense on ADC maps. DW imaging and ADC values have been demonstrated to be useful tools in evaluating the diagnostic accuracy of PCa, which varies in different studies . DW imaging plays an important role in assessing the aggressiveness of PCa by correlating ADC value with Gleason grade . The correlation of ADC values with Ki-67 SI has not been systematically investigated. The purpose of this study was to investigate the relationship between ADC values and Ki-67 SI in PCa.
Materials and methods
Patients
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MRI Protocols
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Pathological Analysis
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Immunohistochemical Analysis of Ki-67
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MRI Analysis
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meanADC=(∑ni=1ADCiSi)/∑ni=1Si mean
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Statistical Analysis
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Results
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Table 1
Distribution and ADC Values of Patients with Ki-67 SI by the 3.5% and 7.1% Cutpoint
Ki-67 SI (%) Gleason score ∗ Number of patients ADC value(×10 −3 mm 2 /s)P value 5 6 7 8 9 ≤3.5 4 4 7 0 0 15 (34.9%) 0.936 ± 0.208 .031 >3.5 0 0 19 5 4 28 (65.1%) 0.803 ± 0.094 ≤7.1 4 4 15 0 1 24 (55.8%) 0.906 ± 0.178 .004 >7.1 0 0 11 5 3 19 (44.2%) 0.779 ± 0.081
ADC, apparent diffusion coefficient; SI, staining index.
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Discussion
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Conclusions
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Acknowledgment
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