Functional MR Imaging Assessment of Tumor Response after ⁹⁰Y Microsphere Treatment in Patients with Unresectable Hepatocellular Carcinoma

Purpose: To assess the utility of functional contrast medium-enhanced and diffusion-weighted magnetic resonance (MR) imaging in the assessment of early (1 month) response of unresectable hepatocellular carcinoma (HCC) to a single treatment with yttrium-90-labeled microspheres. Materials and methods: The authors evaluated the MR images obtained before and 1 month after single selective ⁹⁰Y microsphere treatment in 13 consecutive patients (mean age, 62 years). All patients had cirrhosis and pathologically proved HCC. Images were evaluated by consensus of two radiologists. Tumor size, arterial and venous enhancement, and apparent diffusion coefficient (ADC) were recorded before and after treatment. One targeted tumor in the treated lobe of the liver was included in each patient. In patients who also had lesions in the contralateral lobe of the liver, a second tumor was included as nontargeted tumor. Results: There were 19 tumors in the 13 patients (mean tumor size, 9.4 cm). The mean tumor burden was 25% of the total liver volume. Targeted tumors (n = 13) demonstrated a mean decrease in arterial enhancement of 22% (P = .013), a mean decrease in venous enhancement of 25% (P = .012), and a mean increase in ADC value of 18% (P < .001). These targeted tumors did not change significantly in size after treatment (P = .492). Six patients had contralateral nontargeted tumors. These nontargeted tumors had no significant change in size (P = 0.100), arterial enhancement (P = .182), venous enhancement (P = .182), or ADC value (P = .105) after treatment. Conclusions: Early after treatment with ⁹⁰Y microspheres, tumors demonstrated a decrease in enhancement and an increase in ADC, without a statistically significant change in tumor size. These MR findings are useful in the early posttreatment period for assessing treatment response.