Estimation of the stiffness of hepatic metastases of colorectal cancer and surrounding parenchyma by ultrasound elastometry

Objective. To compare the stiffness of hepatic metastases of colorectal cancer and surrounding parenchyma according to shear wave elastometry for further determination of the ablation margin and its control. Materials and methods. The stiffness of 31 hepatic metastases and surrounding parenchyma in 20 patients with colorectal cancer, 13 men and 7 women aged 43 to 84 years, with a mean age of (61.2± 9.9) years, was evaluated by ultrasound elastometry with the determination of tissue stiffness modulus. The primary tumor was localized in the rectum in 2 patients, the colon in 18 patients, including 10 in the sigmoid colon and 8 in the rectosigmoid region. Histologically, 85% of patients had metastases of moderately differentiated (G2) and 10% of patients had metastases of low–grade (G3) tubular adenocarcinoma of the colon. Metachronous metastasis was detected in 75% of patients. Results. The stiffness of metastases ranged from 9.1 to 31.6 kPa, averaged (19.46± 5.15) kPa and was statistically significantly (p< 0.0001) higher than the stiffness of the surrounding parenchyma, which averaged (6.12± 1.12) kPa; the stiffness of metastatic foci was 1.6 to 6.9 times higher than the stiffness of the surrounding parenchyma, with an average of (3.23± 0.94) times. The stiffness of the surrounding parenchyma in patients with ultrasound signs of steatosis (n=12) was statistically significantly (p< 0.0005) higher than in patients with unchanged parenchyma (n= 8) – (6.51± 1.03) and (4.98± 0.27) kPa, respectively. According to the correlation analysis using a linear regression model, a significant inverse relationship (according to the Cheddock scale) with a correlation coefficient of –0.38 was found between the stiffness of metastatic foci and their size, and a direct loose relationship with a correlation coefficient of –0.30 was found between the stiffness of unchanged surrounding parenchyma and metastatic foci. An inverse relationship with a correlation coefficient of –0.30 was found between the stiffness of metastatic foci and the depth of their location. The use of nonlinear regression models was not accompanied by an increase in the value of the correlation coefficient. Conclusions. The stiffness of hepatic metastases of colorectal cancer significantly exceeds the stiffness of the parenchyma around the foci, which can be used to determine the future ablation margin and control its implementation. There is a loose, but noticeable inverse correlation between the stiffness of hepatic metastases of colorectal cancer and their size. The stiffness of the liver parenchyma in patients with ultrasound signs of steatosis is statistically significantly higher than the stiffness of unchanged parenchyma.