Correlation between Spectral CT Parameters and Ki67 Expression in
Hepatocellular Carcinoma
Authors: Xu Long , Yu Sun Feng , Xian Li Gui , Zai Yang Lin , Xiao Zhuo Ying , Xiao Hu Wei Xiao Hu , Wen Xing 
Published: October 2023

aims:
The objective of this study was to analyze the relationship between quantitative parameters of spectral CT and the Ki67 expression index of tumor cells in hepatocellular carcinoma (HCC).

background:
Hepatocellular carcinoma (HCC) is the fifth-most common malignant tumor in the world and the fourth-leading cause of cancer-related deaths. It is the most common primary malignant tumor of the liver, and its incidence rate is rising. The immunohistochemical marker Ki67 is a nuclear antigen related to cell proliferation activity and is commonly used as an indicator of cell proliferation levels. In recent studies, Ki67 has been recognized as the most valuable independent predictor of early recurrence and poor prognosis in patients with HCC after surgical resection. The level of Ki67 expression is crucial for prognosis and treatment decisions. In clinical settings, Ki67 expression is often determined through puncture biopsy or postoperative pathology, which is an invasive examination. If Ki67 could be evaluated before surgery or puncture, it would have positive implications for clinical diagnosis, treatment, and surgical selection. Previous studies have shown that quantitative parameters of spectral CT exhibit a certain degree of correlation with Ki67 expression in lung adenocarcinoma, non-small-cell lung cancer, and colorectal cancer. To date, there have been no reports of correlation between spectral CT and Ki67 expression in HCC.

objective:
The objective of this study was to analyze the relationship between quantitative parameters of spectral CT and the Ki67 expression index of tumor cells in hepatocellular carcinoma (HCC).

method:
Between January 2022 and June 2023, we selected 35 patients with HCC whose condition was confirmed pathologically in our hospital. Inclusion criteria were as follows: 1. no contraindications for enhanced CT scanning; 2. pathological examination performed within two weeks of CT examination; 3. a maximum cross-sectional diameter of the lesion of at least 1 cm. Exclusion criteria were as follows: 1. artifacts in the image; 2. revelation by pathological examination of other types of liver tumors; 3. non-performance of Ki67 testing. In total, 19 patients were selected: 12 males and 7 females, aged from 38 to 72 years, with an average age of (55.5 ± 9.7) years. Among these individuals, Ki67 was highly expressed in 11 cases and lowly expressed in 8 cases. This study was approved by the Ethics Committee of our hospital.
Examination method: Abdominal enhanced CT examination was performed using Neu Viz Glory 256-layer spectral CT from Neusoft; images were obtained in the spectral CT imaging scanning mode. Patients were placed in a supine position, with arms on opposite sides of the head, and scanned while they held their breath after deep inhalation. The scanning range was from diaphragm top to kidney lower pole, with high- and low-energy (140 and 80 kVp) fast switching (0.25 ms), automatic adjustment of tube current, X-ray tube rotating speed of 0.5 s/r, scanning slice thickness of 5 mm, rotation rate of 0.5 s/r, tube current of 600 mAs, pitch of 0.984, and a reconstruction slice thickness of 0.625 mm. Ordinary epigastrium CT scanning was performed first, followed by enhanced scanning. Using a high-pressure syringe, 300mg/ml of iodofol (dose:1.0ml/kg) was injected intravenously through the elbow at a rate of 4.0–5.0 ml/s, and the tube was then flushed with 40mL of saline. The arterial-phase scanning was set to automatically trigger scanning when the monitoring threshold reached 100Hu (taking the descending aorta as the monitoring layer), and the venous-phase scanning was set to begin 30s after the arterial-phase scanning.
Image data extraction: The original images of arterial and venous images were transmitted to a Neusoft workstation for post-processing, and spectral CT analysis software was used for image analysis and processing. Two doctors with more than 5 years of experience in abdominal imaging diagnosis independently took measurements three times without knowing the pathological results, and an average value was obtained. The brightest image of the tumor in the iodine-based map was selected, and a region of interest (ROI) was placed at the center of the tumor and the same layer of descending aorta. The ROI was required to be at least 1/2 of the size of the tumor, and also avoid the cystic necrosis area. To maintain consistency between the ROI position and the size of the measured images in the arterial and venous phases, the iodine concentration (IC) was recorded in the ROIs of the lesion and aorta, and the relative iodine concentration (RIC) (RIC=IClesion/ICdescending aorta) was calculated for the arterial and venous phases, respectively. In a single-energy spectral program, the CT values in the ROIs of the lesions at 40 keV and 70 keV were recorded, and the slope of the spectral curve (λ) was calculated, where λ= (40 keV-70 keV) /(70-30).
Measurement of Ki67 expression: If a liver cancer cell nucleus was stained brownish-yellow, it was determined to be Ki67-positive. The relative quantification method was used to calculate the percentage of Ki67-positive cells in the total number of tumor cells. Individuals with ≥10% positive cells were assigned to the high-expression group, and those with &amp;lt;10% positive cells were assigned to the low-expression group.
Statistical method: SPSS 23 0 statistical software was used for data analysis. The Kolmogorov–Smirov test was used for normality testing. Normal distribution was expressed as mean ± standard deviation, and non-normal distribution was expressed as median (upper and lower quartile). An independent samples t-test (normal distribution) or Mann–Whitney U test (non-normal distribution) was used to compare differences in the quantitative parameters of spectral CT between the high- and low-Ki67 groups. Receiver operating characteristic (ROC) curves were used to evaluate the discriminative efficacy of spectral CT parameters in high- and low-Ki67 groups, and to calculate the area under the curve (AUC), so that specificity and sensitivity could be analyzed. Pearson correlation analysis was used to analyze the correlation between quantitative parameters of spectral CT and Ki67 expression.

result:
Comparison of quantitative parameters of spectral CT between high- and low-Ki67 groups. During the arterial phase, values for ICAP, RICAP, and λAP (where the subscript AP represents the arterial phase) were higher in the high-Ki67 group than in the low-Ki67 group, with P values of 0.01, 0.00, and 0.04, respectively. In the venous phase, values for RICVP and λVP (where the subscript VP represents the venous phase) were higher in the high-Ki67 group than in the low-Ki67 group, with P values of 0.04 and 0.03, respectively, indicating a statistically significant difference. During the venous phase, there was no significant difference in ICVP between the high- and low-Ki67 groups (P&gt;0.05).
Diagnostic efficacy of quantitative parameters of spectral CT in distinguishing between high- and low-Ki67 group. The diagnostic efficacy of AUC, sensitivity, and specificity of spectral CT in high- and low-Ki67 groups in the arterial and venous phases after enhancement are shown in Table 2 and Figure 4. RIC during the arterial phase produced the largest AUC for the two groups (0.89), with a sensitivity of 90.9% and a specificity of 75.0%.
Correlation analysis of quantitative parameters of spectral CT and Ki67. In both arterial and venous phases, IC, RIC, and λ were positively correlated with Ki67 in HCC patients (P &amp;lt; 0.05), with arterial-phase r values of 0.79, 0.82, and 0.56, respectively, and venous-phase r values of 0.47, 0.57, and 0.56, respectively.

conclusion:
We found statistical differences in IC, RIC and λ between two groups of HCC patients with high and low expression of Ki67, and that the efficiency of differentiation between the two groups was highest at the arterial stage. In addition, these parameters were correlated with Ki67 expression, suggesting that quantitative spectral CT parameters can evaluate the expression of Ki67 in HCC. This finding is of potentially high value for clinical application.

other:
Not Applicable