Integration of quantitative MRI and liver function indices to predict early tumor response after stereotactic body...

Early response assessment following stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) is challenging. We prospectively investigated whether changes in diffusion-weighted magnetic resonance imaging (DWI)-derived apparent diffusion coefficient (ADC), tumor markers, and blood-based indices correlated with an early tumor response.

Nineteen patients with 29 HCC lesions underwent SBRT (40 Gy in four fractions). MRI (T2-weighted imaging, diffusion-weighted imaging/ADC, and gadoxetate disodium-enhanced dynamic contrast imaging) and blood tests were scheduled at baseline and at one and three months following SBRT. Tumor response was also assessed at six months using the modified response evaluation criteria in solid tumors (mRECIST) approach. ΔADC was defined as ADC at three months minus baseline ADC. Inter-observer reproducibility of baseline ADC was evaluated using the single-measure intraclass correlation coefficient (ICC).

ΔADC was inversely correlated with changes in tumor size at three months (r = -0.43, p = 0.039). ΔADC correlated with the percent change in des-γ-carboxy prothrombin (PIVKA-II) at three months (r = 0.50, p < 0.01) but not with the percent change in alpha-fetoprotein (AFP, r = 0.14, p > 0.05). Baseline ADC demonstrated good reproducibility (ICC = 0.793; 95% CI, 0.606-0.897). The retention rate of indocyanine green at 15 min and albumin-bilirubin scores remained largely stable throughout the three month period.

Early increases in ADC after SBRT of the liver were associated with tumor shrinkage and changes in PIVKA-II, supporting the use of quantitative MRI as an early response biomarker. Larger cohorts with longer follow-up periods are warranted.