Colorectal liver metastasis after ⁹⁰Y radioembolization therapy: Pilot study of change in MDCT attenuation as a surrogate marker for future FDG PET response

OBJECTIVE. The purpose of this study was to investigate whether changes in attenuation and size of liver metastatic lesions of colorectal cancer at MDCT 1 month after ⁹⁰Y radioembolization treatment are predictive of response at FDG PET 3 months after treatment. MATERIALS AND METHODS. Twenty patients with colorectal liver metastasis consecutively treated with ⁹⁰Y radioembolization underwent triphasic MDCT of the liver at baseline and 1 and 3 months after treatment and FDG PET at baseline and 3 months after treatment. Percentage change in tumor attenuation at MDCT (volumetric attenuation), tumor size at MDCT (according to Response Evaluation Criteria in Solid Tumors [RECIST] and World health Organization [WHO] criteria), and volume-weighted maximum standardized uptake value at FDG PET were evaluated. The correlation between FDG PET response 3 months after treatment and response according to RECIST, WHO criteria, and attenuation 1 month after treatment was evaluated. RESULTS. Only 13.3% of patients with FDG PET findings of response 3 months after treatment were identified according to RECIST and WHO criteria 1 month after treatment. According to attenuation criteria at 1 month, however, 53.3% of patients with an FDG PET response at 3 months were identified. A strong association was found between FDG PET response at 3 months and response based on attenuation criteria (odds ratio, 12.4; 95% CI, 0.58-265.3; p = 0.05). CONCLUSION. Early changes in the attenuation of liver metastatic lesions of colon cancer after ⁹⁰Y radioembolization treatment may be predictive of future response at FDG PET.