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

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 Yttrium90 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/F38/14, 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.