UC San Diego

Background

Magnetic resonance imaging-derived measures of liver fat and volume are emerging as accurate, non-invasive imaging biomarkers in non-alcoholic steatohepatitis (NASH). Little is known about these measures in relation to histology longitudinally.

Aim

To examine any relationship between MRI-derived proton-density fat-fraction (PDFF), total liver volume (TLV), total liver fat index (TLFI), vs. histology in a NASH trial.

Methods

This is a secondary analysis of a 24-week randomised, double-blind, placebo-controlled trial of 50 patients with biopsy-proven NASH randomised to oral ezetimibe 10 mg daily (n = 25) vs. placebo (n = 25). Baseline and post-treatment anthropometrics, biochemical profiling, MRI and biopsies were obtained.

Results

Baseline mean PDFF correlated strongly with TLFI (Spearman's ρ = 0.94, n = 45, P < 0.0001) and had good correlation with TLV (ρ = 0.57, n = 45, P < 0.0001). Mean TLV correlated strongly with TLFI (ρ = 0.78, n = 45, P < 0.0001). After 24 weeks, PDFF remained strongly correlated with TLFI (ρ = 0.94, n = 45, P < 0.0001), maintaining good correlation with TLV (ρ = 0.51, n = 45, P = 0.0004). TLV remained strongly correlated with TLFI (ρ = 0.74, n = 45, P < 0.0001). Patients with Grade 1 vs. 3 steatosis had lower PDFF, TLV, and TLFI (P < 0.0001, P = 0.0003, P < 0.0001 respectively). Regression analysis of changes in MRI-PDFF vs. TLV indicates that 10% reduction in MRI-PDFF predicts 257 mL reduction in TLV.

Conclusions

The MRI-PDFF and TLV strongly correlated with TLFI. Decreases in steatosis were associated with an improvement in hepatomegaly. Lower values of these measures reflect lower histologic steatosis grades. MRI-derived measures of liver fat and volume may be used as dynamic and more responsive imaging biomarkers in a NASH trial, than histology.