Lin XJ, Zhu S, Wang D, Chen JY, Wei SX, Chen SY, Luo HC. Correlation of dynamic contrast-enhanced ultrasonography and the Ki-67 labelling index in pancreatic ductal adenocarcinoma. World J Gastroenterol 2024; 30(44): 4697-4708 [PMID: 39610780 DOI: 10.3748/wjg.v30.i44.4697]
Corresponding Author of This Article
Hong-Chang Luo, PhD, Director, Doctor, Department of Medical Ultrasound, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 1095 Jiefang Avenue, Qiaokou District, Wuhan 430030, Hubei Province, China. hongchangluo@qq.com
Research Domain of This Article
Radiology, Nuclear Medicine & Medical Imaging
Article-Type of This Article
Retrospective Study
Open-Access Policy of This Article
This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Xiao-Jing Lin, Shu Zhu, Dan Wang, Jing-Yuan Chen, Su-Xian Wei, Shi-Yun Chen, Hong-Chang Luo, Department of Medical Ultrasound, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei Province, China
Author contributions: Lin XJ, Zhu S, Wang D, Chen JY, Wei SX, Chen SY and Luo HC designed the research study; Lin XJ, Zhu S, Wang D and Luo HC performed the research; Lin XJ, Chen JY, Wei SX and Chen SY analyzed the data; Lin XJ, Zhu S, Wang D, Chen JY and Luo HC wrote the manuscript; All authors have read and approved the final manuscript.
Institutional review board statement: This study was approved by the Ethics Committee of Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. TJ-IRB202402131.
Informed consent statement: The need for patient consent was waived due to the retrospective nature of the study.
Conflict-of-interest statement: The authors declare that they have no conflict of interest.
Data sharing statement: All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Hong-Chang Luo, PhD, Director, Doctor, Department of Medical Ultrasound, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 1095 Jiefang Avenue, Qiaokou District, Wuhan 430030, Hubei Province, China. hongchangluo@qq.com
Received: May 20, 2024 Revised: September 22, 2024 Accepted: October 23, 2024 Published online: November 28, 2024 Processing time: 175 Days and 17 Hours
Abstract
BACKGROUND
Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant and aggressive tumor, and high Ki-67 expression indicates poor histological differentiation and prognosis. Therefore, one of the challenges in diagnosing preoperatively patients with PDAC is predicting the degree of malignancy. Dynamic contrast-enhanced ultrasonography (DCE-US) plays a crucial role in abdominal tumor diagnosis, and can adequately show the microvascular composition within the tumors. However, the relationship between DCE-US and the Ki-67 labelling index remains unclear at the present time.
AIM
To predict the correlation between Ki-67 expression and the parameters of DCE-US.
METHODS
Patients with PDAC who underwent DCE-US were retrospectively analyzed. Patients who had received any treatment (radiotherapy or chemotherapy) prior to DCE-US; had incomplete clinical, imaging, or pathologic information; and had poor-quality image analysis were excluded. Correlations between Ki-67 expression and the parameters of DCE-US in patients with PDAC were assessed using Spearman’s rank correlation analysis. The diagnostic performances of these parameters in high Ki-67 expression group were evaluated according to receiver operating characteristic curve.
RESULTS
Based on the Ki-67 labelling index, 30 patients were divided into two groups, i.e., the high expression group and the low expression group. Among the relative quantitative parameters between the two groups, relative half-decrease time (rHDT), relative peak enhancement, relative wash-in perfusion index and relative wash-in rate were significantly different between two groups (P = 0.018, P = 0.025, P = 0.028, P = 0.035, respectively). The DCE-US parameter rHDT was moderately correlated with Ki-67 expression, and rHDT ≥ 1.07 was more helpful in accurately diagnosing high Ki-67 expression, exhibiting a sensitivity and specificity of 53.8% and 94.1%, respectively.
CONCLUSION
One parameter of DCE-US, rHDT, correlates with high Ki-67 expression. It demonstrates that parameters obtained noninvasively by DCE-US could better predict Ki-67 expression in PDAC preoperatively.
Core Tip: The Ki-67 labelling index reflects the proliferation of tumor cell and it can only be obtained using puncture biopsy or surgical resection. Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant and aggressive tumor. Few studies on preoperative prediction of Ki-67 expression in PDAC using dynamic contrast-enhanced ultrasonography (DCE-US) have been conducted. Our results demonstrate that DCE-US helps noninvasively predict Ki-67 expression preoperatively in PDAC and it is valuable for surgeons to make clinical treatment program and assess prognosis.
Citation: Lin XJ, Zhu S, Wang D, Chen JY, Wei SX, Chen SY, Luo HC. Correlation of dynamic contrast-enhanced ultrasonography and the Ki-67 labelling index in pancreatic ductal adenocarcinoma. World J Gastroenterol 2024; 30(44): 4697-4708
According to the American Cancer Society, pancreatic ductal adenocarcinoma (PDAC) caused an estimated 62210 new cases and 49830 deaths in 2022 in the United States, with a 5-year overall survival rate of approximately 10%[1,2]. PDAC is the most common malignant tumor among pancreatic space-occupying lesions. However, owing to the insidious onset and lack of specific symptoms, early diagnosis of PDAC is difficult, delaying the optimal time for treatment and resulting in a poor prognosis.
Ki-67 is a nuclear antigen that is highly expressed in the active phase of the cell cycle and negatively expressed in the resting phase (G0)[3]. The Ki-67 labelling index reflects the proliferation of tumor cells, and a high expression of Ki-67 indicates a higher degree of tumor malignancy, which correlates with poorer prognosis and shorter patient survival[4,5]. Moreover, studies are increasingly using the Ki-67 labelling index as a biomarker of therapeutic efficacy[6]. Nevertheless, the Ki-67 labelling index merely obtains using puncture biopsy or surgical resection. Therefore, being able to rapidly, non-invasively and accurately predict the Ki-67 labelling index is necessary.
Contrast-enhanced ultrasonography (CEUS) can show microcirculatory perfusion within lesions and it has the advantages of being real-time, dynamic, and non-invasive. The EFSUMB guidelines suggest that CEUS can improve the diagnostic performance of pancreatic space-occupying lesions, especially for the evaluation of intralesional and perilesional vascular visualization[7]. Dynamic contrast-enhanced ultrasonography (DCE-US) can accurately provide angiogenic information on dynamic changes in contrast agents and quantify vascular perfusion inside lesions[8,9]. Previous studies have shown that DCE-US is widely used to predict microvascular infiltration and assess the efficacy of antiangiogenic therapy[8,10-12]. However, few studies exist on the use of transabdominal DCE-US for the preoperative prediction of the Ki-67 expression in PDAC. Most of the current studies have focused on computed tomography (CT) or magnetic resonance imaging (MRI)[13,14]. Therefore, in this study, we sought to explore the correlation between the parameters of DCE-US and the Ki-67 expression to clarify the degree of malignancy of PDAC for clinicians preoperatively.
MATERIALS AND METHODS
Patients
This study was approved by the Ethics Committee of our hospital. As the study was retrospective, it waived to obtain informed consent from the patients. We analyzed data from patients with a pathologically confirmed PDAC between August 2023 and February 2024 in this retrospective study. The inclusion criteria were as follows: (1) PDAC confirmed by puncture biopsy or surgical resection; (2) The Ki-67 labelling index obtained by immunohistochemistry; and (3) Patients not receiving local or systemic therapy prior to CEUS. The exclusion criteria were as follows: (1) The patient received any treatment (radiotherapy or chemotherapy) prior to CEUS; (2) Incomplete clinical, imaging or pathological information; and (3) Poor quality of images for analysis.
The 30 patients included in this study consisted of 18 males (60%) and 12 females (40%). Of the 30 patients included, 13 and 17 were in the high (Ki-67 ≥ 50%) and low (Ki-67 < 50%) expression groups, respectively (Figure 1).
Figure 1 Flowchart of the study population.
PDAC: Pancreatic ductal adenocarcinoma; CEUS: Contrast-enhanced ultrasonography.
Histopathological evaluation
All patients underwent immunohistochemical analysis to obtain the Ki-67 labelling index, which was positive when the nuclei stained brownish-yellow. Ki-67 levels were determined using the percentages of immunoreactive cells from 1000 malignant cells and scoring areas in the tumor with the highest number of positive nuclei (hot spots). The results of the Ki-67 analysis were classified as continuous data ranging from 0% to 100%. As the optimal cutoff value for the Ki-67 index was not determined, 50% was chosen in this study as the threshold based on previous studies[5,13,15].
The CEUS inspection process
CEUS was performed using the Logic E9 US system (GE Healthcare) with a convex array probe. The frequency of the transducers ranged from 2 to 5 MHz. Each patient continuously fasted at least 8 hours and underwent gray-scale ultrasonography, color Doppler ultrasonography, and CEUS. An experienced radiologist performed all ultrasound examinations. SonoVue (Bracco) was dissolved in 5.0 mL of saline. Suspension (2.0 mL) of SonoVue mixed with saline was injected via the antecubital vein, and flushed the vein with 5.0 mL of normal saline. Timing was initiated immediately after contrast injection, and the digital imaging and communications in medicine images of CEUS were stored continuously for 150 seconds for further analysis.
Quantitative analysis
Quantitative analysis was performed using a NovoUltrasound Kit (version 1.5.0, GE Healthcare, Shanghai, China). The 150 seconds CEUS images were transferred to an offline computer for further analysis. Quantitative analysis was performed by an abdominal radiologist with two years of experience who was blinded to the pathological diagnosis. The regions of interest (ROI) were manually placed in the solid component of lesions and surrounding parenchyma. The ROIs for the lesion and parenchyma were selected at the same depth, as much as possible. Motion compensation was used to minimize the effects of respiratory artefacts. The generated time-intensity curves (TIC) reflect the dynamic course of contrast agent within the ROIs. To minimize the influence of different ROI lesion depths on the results in different patients, the ratios of the quantitative parameters of a solid pancreatic lesion to those of surrounding normal pancreatic parenchyma were calculated. Consequently, the parameters obtained were relative contrast agent arrival time, relative peak enhancement (rPE), relative half-decrease time (rHDT), relative fall time, relative rise time, relative time to peak, relative wash-in area under the curve, relative wash-in perfusion index (rWiPI), relative wash-in rate (rWiR), relative wash-out area under the curve, relative wash-out rate (rWoR), relative wash-in and wash-out area under the curve (rWiWoAUC), and relative mean transit time (Table 1 and Figure 2).
Figure 2 Dynamic contrast-enhanced ultrasonography perfusion analysis on patients with pancreatic ductal adenocarcinoma confirmed by histopathology.
Regions of interest of the pancreatic ductal adenocarcinoma lesion (orange circle) and surrounding pancreatic parenchyma (blue circle) were placed manually and the time-intensity curves were obtained. A and B: A 52-year-old female with a pancreatic ductal adenocarcinoma lesion (the Ki-67 labelling index of 60%); C and D: A 67-year-old male with a pancreatic ductal adenocarcinoma lesion (the Ki-67 labelling index of 20%). TIC: Time-intensity curve.
Maximum enhancement intensity during the arterial phase
Half-decrease time (second)
The time required to decrease from PE to 1/2 PE of the arterial phase
Fall time (second)
The time for the contrast agent intensity to decrease from 95% to 5% of PE during the arterial phase
Rise time (second)
The time it takes for the contrast agent intensity to go from 5% to 95% of PE during the arterial phase
Time to peak (second)
The time required to reach PE of the arterial phase after contrast agent injection
Wash-in area under the curve (a.u.)
Area under the TIC from the time of arrival to the PE of arterial phase
Wash-in perfusion index (a.u./second)
WiAUC/RT
Wash-in rate (a.u./second)
The maximum slope of the rising part of the TIC
Wash-out area under the curve (a.u.)
The area under the TIC from the PE of the arterial phase to the end of the curve
Wash-out rate (a.u./second)
The minimum slope of the descending part of the curve
Wash-in and wash-out area under the curve (a.u.)
WiAUC + WoAUC, representing the area under the entire curve
Mean transit time (second)
Time from the rising of the intensity up to decrease to 50% of maximum
Statistical analysis
Statistical analyses were performed using IBM SPSS statistics (version 25.0). Continuous variables were expressed as mean ± SD or median (25th and, 75th percentile), and categorical variables were expressed as numbers and percentages. Continuous variables were estimated using the t-test or Mann-Whitney U test. Categorical variables were estimated using Fisher’s exact test. Spearman’s rank correlation analysis was used to compare the correlation between the DCE-US parameters of patients with PDAC and the Ki-67 index. The diagnostic efficacy of the DCE-US parameters for high Ki-67 expression was evaluated using the receiver operating characteristic curve (ROC). Specificity and sensitivity were calculated for the area under the curve (AUC). Statistical significance was set at P < 0.05.
RESULTS
Clinical characteristics and gray-scale ultrasonography
Age, gender, body mass index, and prevalence of diabetes mellitus were not significantly different between these two groups (P > 0.05). Patients in both groups mostly exhibited solid hypoechoic lesions on gray-scale ultrasonography. No statistically significant differences were observed between the two groups in terms of tumor size, location, echogenicity, margin, shape, and main pancreatic duct dilation (P > 0.05). Conversely, the presence or absence of blood flow signals between the two groups was a statistically significant difference (P = 0.033) (Table 2).
Table 2 Clinical data and gray-scale ultrasonography characteristics of the patients, n (%).
Performing further quantitative analysis, the quantitative parameters PE, wash-in AUC (WiAUC), WiPI, WiR, WiWoAUC, WoAUC, and WoR of the lesions in the high Ki-67 expression group were significantly different from those of surrounding normal pancreatic parenchyma (P < 0.05). The WiWoAUC of the lesions in the low Ki-67 expression group was significantly different from that of surrounding normal pancreatic parenchyma (P < 0.05). In contrast, no statistically significant differences in the PE, WiAUC, WiPI, WiR, WoAUC, and WoR of the lesions in the low Ki-67 expression group were observed (P > 0.05); However, these parameters were lower than those of the surrounding normal pancreatic parenchyma (Table 3).
Table 3 Comparison of quantitative parameters between the pancreatic ductal adenocarcinoma lesions and pancreatic parenchyma.
To minimize the influence of different ROI depths on the results, relative quantitative parameters were used to compare the two groups. Comparing the relative quantitative parameters between the two groups, we concluded that rHDT, rPE, rWiPI and rWiR were significantly different between the two groups (P < 0.05) (Table 4).
Table 4 Comparison of relative quantitative parameters between the high and low Ki-67 expression groups.
Correlation between DCE-US and the Ki-67 expression
Spearman’s rank correlation analysis showed that rHDT was positively correlated with Ki-67 expression (r = 0.439, P = 0.015). In contrast, rPE, rWiPI, and rWiR negatively correlated with Ki-67 expression (r = -0.416, P = 0.022; r = -0.408, P = 0.025; r = -0.392, P = 0.032) (Table 5).
Table 5 Correlation study of quantitative dynamic contrast-enhanced ultrasonography parameters with Ki-67 expression in patients with pancreatic ductal adenocarcinoma.
ROC of quantitative parameters to identify Ki-67 expression
Further ROC analysis was performed to assess the diagnostic efficacy of the quantitative DCE-US parameters. The relative quantitative DCE-US parameter, rHDT, was the most helpful in accurately diagnosing high Ki-67 expression. The AUC for rHDT was 0.756, with a cutoff value of 1.07. Although its diagnostic sensitivity was low (53.8%), its specificity was 94.1% (Figure 3 and Table 6).
Figure 3 Diagnostic efficacy of relative half-decrease time for differentiating between the high group and low Ki-67 expression groups.
The relative half-decrease time ≥ 1.07 was more helpful in accurately predicting high Ki-67 expression. ROC: Receiver operating characteristic curve.
Table 6 Parameter of receiver operating characteristic curves.
Ki-67 protein can predict tumor aggressiveness and risk of recurrence, and preoperative assessment of PDAC proliferative activity can help guide treatment strategies and assess prognosis. In this retrospective study, we analyzed the relationship between the quantitative parameters obtained using DCE-US and Ki-67 expression. We found that, in the high Ki-67 expression group, some parameters of lesions were significantly different from those of the normal pancreatic parenchyma. High Ki-67 expression was correlated with rHDT, rPE, rWiPI, and rWiR. Based on further analysis, rHDT ≥ 1.07 may be a valid quantitative parameter for the preoperative prediction of PDAC with the high Ki-67 expression.
Patients with PDAC have an extremely poor prognosis and a low survival rate owing to its aggressive biology[16]. As a well-known biomarker, the Ki-67 antigen is a vital tumor proteogenomic component that responds to tumor heterogeneity and accurately reflects tumor cell proliferation and aggressive biology. Some studies have demonstrated the correlation between the Ki-67 labelling index and prognosis. Atrash et al[17] retrospectively analyzed 167 patients with multiple myeloma and they concluded that patients in the bone marrow high Ki-67 labelling index (> 5%) group were at higher risk of progression or death. Meng et al[18] analyzed patients with rare malignant tumors originating from the endometrial mesenchyme (i.e., endometrial mesenchymal sarcoma), and their results showed that the high Ki-67 labelling index was significantly associated with recurrence of endometrial mesenchymal sarcoma and was an independent prognostic factor for endometrial mesenchymal sarcoma. Therefore, high Ki-67 expression indicates poorly differentiated and more aggressive tumor histology and worse prognosis[5,13].
The Ki-67 labelling index is only available for tumor tissue specimens obtained by surgical resection or puncture biopsy, limiting its usefulness; Endoscopic ultrasound-guided fine-needle aspiration is considered a safe and effective diagnostic tool for obtaining pathological tissue for pancreatic occupations[19]. However, this method requires a reasonable amount of tissue specimen, requires a high degree of skill on the part of the endoscopist, and is invasive. Moreover, PDAC is a low tumor cell type tumor with only 5%-20% tumor cell counts, making it even more challenging for tissue analysis by endoscopic ultrasound-guided fine-needle aspiration[20]. Therefore, identifying noninvasive imaging that effectively and rapidly predicts Ki-67 expression in clinical applications is essential. Some studies have shown that radiological findings are the good predictor of the Ki-67 expression. Nie et al[21] analyzed non-mass-enhancing breast cancer using dynamic contrast-enhanced MRI features with apparent diffusion coefficient values, and concluded that apparent diffusion coefficient values and TIC type were correlated with Ki-67 expression. Zheng et al[22] also concluded that it was a good predictor of the Ki-67 index in patients with head and neck squamous cell carcinoma using a CT radiomics nomogram.
With the development of ultrasonography, CEUS has played an important role in the diagnosis of pancreatic diseases and has advantages in predicting responses to therapy and disease staging[7]. Fan et al[23] analyzed 90 cases of solid pancreatic space-occupying lesions and concluded that the diagnosis of pancreatic carcinoma and focal pancreatitis using CEUS were similar to those using contrast-enhanced CT. Lu et al[24] performed DCE-US in patients with locally advanced PDAC and concluded that it could quantify microvascular perfusion and visualize the effects of tumor chemoradiotherapy. Wang et al[25] proposed five CEUS enhancement modalities to noninvasively reflect the preoperative tumor vascularization information of PDAC for a better prediction of early recurrence after curative resection and strict management of postoperative follow-up.
To date, few studies have been conducted to predict the Ki-67 expression capacity in PDAC preoperatively using DCE-US. We used DCE-US to display microcirculatory perfusion inside the lesion dynamically and in real-time, thus providing accurate quantification of intratumoral perfusion. Our study found significant differences in the parameters PE, WiAUC, WiPI, WiR, WiWoAUC, WoAUC, and WoR between PDAC and surrounding normal pancreatic parenchyma in the high Ki-67 expression group. However, only the WiWoAUC was significantly different in the low Ki-67 expression group. No statistically significant differences were observed in the low Ki-67 expression group for the parameters indicating contrast agent wash-in (PE, WiPI, and WiR), which may be due to small sample size and data collection errors, but those of the high Ki-67 expression group (5.31 × 107 a.u., 3.32 × 107 a.u./second, and 6.40 × 106 a.u./second, respectively) were significantly lower than those of the low Ki-67 expression group (8.05 × 107 a.u., 5.07 × 107 a.u./second, and 9.63 × 106 a.u./second). Our findings are consistent with those of Wen et al[26], in which the normalized iodine concentration, which objectively reflects iodine deposition, and the extracellular volume fraction, which reflects extravascular and extracellular spaces, were significantly lower in the high expression group than in the low expression group. Yang et al[27] also predicted histopathological grading by quantitative microvascular perfusion in patients with pancreatic neuroendocrine tumors (pNETs). In their study, they showed a higher micro-vessel density but a relatively low fibrotic component in pNETs G1/G2[27]. PDAC is a tumor that lacks blood supply and is characterized by extracellular mesenchymal deposition, massive fibrosis, and few tumor micro-vessels, resulting in a hypoxic tumor microenvironment. Moreover, facilitative glucose transporter-1 is highly expressed in the hypoxic environment, which further promotes glycolysis and is more conducive to the proliferation of infiltrating tumor cells[28-30]. Compared with the low Ki-67 expression group, this may lead to poorer vascularization, heavier internal ischemic and hypoxic microenvironment, and higher proportion of internal fibrous matrix in the high Ki-67 protein expression group.
To minimize the effect of confounding factors, we also performed a correlation analysis between relative DCE-US quantitative parameters and Ki-67 expression (Ki-67 index ≥ 50% vs < 50%). We found that rPE, rWiPI, and rWiR were negatively correlated with high Ki-67 expression, while rHDT was positively correlated with high Ki-67 expression. Further ROC analysis was performed, and the relative quantitative parameter rHDT ≥ 1.07 was found to be a valid indicator of preoperative noninvasive prediction of high Ki-67 expression group in patients with PDAC. HDT is defined as the time required to decrease from PE to 1/2 PE of the arterial phase, and reflects the degree of contrast wash-out. Unlike other solid tumors, PDAC has a desmoplastic reaction within its focal microenvironment, which is a key factor in its development. One theory suggested that internal blood circulation of PDAC is reduced because of the large amount of extracellular matrix and collagen deposits within it, resulting in compression of the tumor’s microvasculature[31]. Therefore, the high Ki-67 expression group of PDAC had a higher degree of fibrosis, ischaemia and hypoxia in the internal tumor microenvironment, and microcirculatory perfusion in the high Ki-67 expression group was relatively slower than that in the low Ki-67 expression group. However, this hypothesis requires further investigation. Ma et al[32] analyzed microvascular perfusion in diabetic kidney injury using DCE-US. Due to diabetic renal injury, along with features such as thickening of the intima layer, hyalinization of small arteries, and atherosclerosis, renal capillaries become narrow or even occluded in later stage. The Goto-Kakizaki (GK) rat group had longer HDT than that of the control group, and as glomerulosclerosis worsened, the 20-week-old GK rats also had longer HDT than that of the 4-week-old and 12-week-old rats[32]. Our results were consistent with the above findings in that rHDT was significantly longer in the high Ki-67 expression group than in the low Ki-67 expression group. Thus, we conclude that PDAC with the relative parameter rHDT ≥ 1.07 had more active tumor cell proliferation, more aggressive biological features, and a high risk of poor prognosis.
This study has some limitations. First, this was a single-center study with a small sample size. In future, studies with a larger sample size are needed, and the relationship of the application of DCE-US in analyzing the Ki-67 expression in patients with PDAC should be further validated by a multicenter prospective study at a later stage. Second, this was a retrospective study, which has the potential for selection bias. Third, because the optimal cutoff value for the Ki-67 index is unknown, we subjectively chose Ki-67 ≥ 50% as the cutoff value based on previous studies, but other studies that have chosen other critical values, and this study did not explore the different critical values. Finally, the follow-up period of this study was short, and the value of predicting the prognostic situation of patients with PDAC by DCE-US requires further validation.
CONCLUSION
Our study revealed significant differences in rHDT, rPE, rWiPI, and rWiR between the high and low Ki-67 expression groups. Additionally, rHDT was more helpful in predicting the Ki-67 expression in patients with PDAC. Taken together, these findings demonstrate the good performance of DCE-US in predicting the Ki-67 expression in PDAC patients. This noninvasive method may help surgeons to formulate therapeutic strategies and determine the prognosis in the preoperative period.
ACKNOWLEDGEMENTS
The authors gratefully acknowledge with gratitude all staff members who participated in this study.
Footnotes
Provenance and peer review: Unsolicited article; Externally peer reviewed.
Peer-review model: Single blind
Specialty type: Gastroenterology and hepatology
Country of origin: China
Peer-review report’s classification
Scientific Quality: Grade B, Grade B
Novelty: Grade A, Grade B
Creativity or Innovation: Grade B, Grade B
Scientific Significance: Grade A, Grade A
P-Reviewer: Abdal TA; Geng YQ S-Editor: Fan M L-Editor: A P-Editor: Guo X
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