Value of tumor stiffness measured with MR elastography for assessment of response of hepatocellular carcinoma to locoregional therapy

Abstract

Purpose: The aim of the study was to correlate tumor stiffness (TS) measured with MR elastography (MRE) with degree of tumor enhancement and necrosis on contrast-enhanced T1-weighted imaging (CE-T1WI) in hepatocellular carcinomas (HCC) treated with Yttrium-90 radioembolization (RE) or transarterial chemoembolization plus radiofrequency ablation (TACE/RFA).

Material and methods: This retrospective study was IRB-approved and the requirement for informed consent was waived. 52 patients (M/F 38/14, mean age 67 years) with HCC who underwent RE (n = 22) or TACE/RFA (n = 30) and 11 controls (M/F 6/5, mean age 64 years) with newly diagnosed untreated HCC were included. The MRI protocol included a 2D MRE sequence. TS and LS (liver stiffness) were measured on stiffness maps. Degree of tumor necrosis was assessed on subtraction images by two observers, and tumor enhancement ratios (ER) were calculated on CE-T1WI by one observer.

Results: 63 HCCs (mean size 3.2 ± 1.6 cm) were evaluated. TS was significantly lower in treated vs. untreated tumors (3.9 ± 1.8 vs. 6.9 ± 3.4 kPa, p = 0.006) and also compared to LS (5.3 ± 2.2 kPa, p = 0.002). There were significant correlations between TS and each of enhancement ratios (r = 0.514, p = 0.0001), and percentage of necrosis (r = -0.540, p = 0.0001). The observed correlations were stronger in patients treated with RE (TS vs. ER, r = 0.636, TS vs. necrosis, r = -0.711, both p = 0.0001). Percentage of necrosis and T1-signal in native T1WI were significant independent predictors of TS (p = 0.0001 and 0.001, respectively).

Conclusion: TS measured with MRE shows a significant correlation with tumor enhancement and necrosis, especially in HCCs treated with RE.

Keywords: Hepatocellular carcinoma; Locoregional therapy; MR elastography; Tumor stiffness.

Figure 1

Boxplots showing measurements of tumor stiffness (TS) in untreated and treated HCCs and background cirrhotic liver (Liver) (A), tumor stiffness (TS) in HCCs with <50% necrosis and ≥50% necrosis (B) and tumor stiffness (TS) in HCCs with either isointense, hypointense or hypointense with hyperintense rim (other) or hyperintense signal on native T1-weighted images (T1WI).

Figure 2

Scatterplots show Pearson correlation between HCC tumor stiffness values measured with MRE and visually assessed degree of tumor necrosis (r= -0.540, P= 0.0001) (A) and enhancement ratios (r= 0.514, P= 0.0001) (B), respectively. The observed correlations were stronger in the group of patients treated with RE (r= -0.771, P= 0.0001) (C) and (r= 0.636, P= 0.0001) (D), respectively.

Figure 3

67-year-old male patient with HCV cirrhosis and untreated infiltrative HCC in left hepatic lobe. HCC (arrows) shows hypointense signal on native T1-weighted images (T1WI) (A) and hyperenhancement on contrast-enhanced T1WI obtained during arterial phase (B). Subtraction images (C) were analyzed for diagnosis of necrosis. Wave image (D) demonstrates excellent wave propagation through the tumor, with longer wavelength in tumor compared to surrounding liver parenchyma. Stiffness map (E) demonstrates visually higher stiffness in HCC vs. liver parenchyma (stiffness values were 11.6 kPa in HCC and 4.0 kPa in liver). HCC is well visualized on elastogram color map (F).

Figure 4

63-year-old female patient with HCV cirrhosis and HCC in left hepatic lobe (segment 4) treated with ⁹⁰ Yttrium radioembolization. HCC (arrows) shows hypointense signal on native T1-weighted images (T1WI) (A) and no enhancement on contrast-enhanced T1WI in during arterial phase (B). Subtraction image (C) shows 100% necrosis. Wave image (D) demonstrates excellent wave propagation through the tumor, with shorter wavelength in tumor compared to surrounding liver parenchyma. Stiffness map (E) demonstrates visually lower stiffness in HCC vs. liver parenchyma (stiffness values were 2.6 kPa in HCC and 7.4 kPa in liver). Treated HCC is visualized on elastogram color map (F).

Figure 5

56-year-old male patient with HCV cirrhosis and HCC in right hepatic lobe treated with transarterial chemoembolization plus radiofrequency ablation. HCC (arrows) shows hyperintense signal on native T1-weighted images (T1WI) (A) compatible with hemorrhagic changes post treatment, and no enhancement on contrast-enhanced T1WI during arterial phase (B). Subtraction image (C) shows complete tumor necrosis. Wave image (D) demonstrates excellent wave propagation through the tumor, with longer wavelength in tumor compared to surrounding liver parenchyma. Stiffness map (E) demonstrates visually higher stiffness in HCC vs. liver parenchyma (stiffness values were 7.3 kPa in HCC and 4.7 kPa in liver). Treated HCC is visualized on elastogram color map (F).