Early therapy response assessment by apparent diffusion coefficient (ADC) quantification following glass-based yttrium-90 radioembolization for unresectable hepatocellular carcinoma (HCC).

Abstract

e15140 Background: Early objective imaging biomarker assessment of infiltrative HCC following Y90 radioembolization is not well understood. Early diffusion weighted imaging (DWI) of treated lesions was evaluated and correlated with anatomical treatment response using modified response evaluation criteria in solid tumors (mRECIST). Methods: In an IRB approved prospective proof of concept study, 10 consecutive patients (89% men, median age 55) with unresectable infiltrative HCC and portal vein thrombosis underwent Y90. MR imaging was obtained pre-Y90, 1 and 3 months post-Y90. DWI fat-suppressed single-shot echo-planar sequence with tri-directional diffusion gradient was performed (b=50,400,800 s/mm2). Using pixel-based ADC maps, mean values of treated lesions and surrounding tumor-free liver were measured by manually drawing a noncircular region of interest around corresponding areas on the same image slice. Treatment response was evaluated using mRECIST with complete response as non-enhancement of treated lesion. T-test was performed using SPSS Statistics v20.0 (IBM, Armonk, NY) and significance set at < 0.05. Results: On 30 day post therapy MR and based on mRECIST, 70% of patients had objective response (CR=30%, PR=40%, SD=20%, PD=10%). Mean pre and post-Y90 ADC value of cancer-free liver was 1.10 × 10−3 and 1.08 × 10−3 mm2/sec (p=0.65). Mean ADC value of all treated tumors pre and post-Y90 was 0.82 × 10−3 and 1.19 × 10−3 mm2/sec respectively (p <0.001). Correlating with mRECIST treatment response, mean post-Y90 ADC of lesions with objective and those with no objective response were 1.03 × 10−3 mm2/sec and 1.26 × 10−3 mm2/sec respectively (p=0.003). While there was a significant difference between ADC values of lesion with objective response vs. others, no significant difference was observed at baseline ADC of tumors with eventual objective response vs. others. Corresponding ADC values on 30 and 90 day followup scans were unchanged. Conclusions: Mean ADC value measured 30-days post-therapy shows promises as an objective imaging biomarker to assess treatment response following Y90 therapy for infiltrative HCC.