AIM:To evaluate the response to treatment in patients with neuroendocrine tumor liver metastases following yttrium-90 ( 90 Y) radioembolotherapy, as a function of image patterns at presentation for 90 Y radioembolotherapy. METHODS: The study cohort consisted of patients with hepatic metastatic neuroendocrine tumors treated with 90 Y at our institution during a two-year time period. Hepatic metastases were evaluated on a pretherapy study assessing relative arterial enhancement compared to liver, lesion size, necrosis of the lesion, and associated tumor burden in the liver. We used six response criteria: Response Evaluation Criteria in Solid Tumors (RECIST) size, World Health Organization (WHO) size, European Association for the Study of the Liver (EASL) necrosis guidelines, Choi size, Choi necrosis and combination of Choi size and necrosis. RESULTS: About 65 lesions in 17 patients met study criteria and formed the cohort. Statistically significant response was found for lesions < 5 cm vs those ≥5 cm with RECIST (P = 0.04), WHO (P = 0.002) and combined Choi criteria (P = 0.02). Hyperenhancing lesions demonstrated greater response only with the Choi size criteria (P = 0.04). Lesions with ≤ 50% necrosis on the pre-scan had statistically significant greater response with the Choi necrosis criteria (P = 0.01). There was no statistical significance for response comparing lesions < 2 cm vs ≥ 2 cm or in comparing the degrees of tumor burden. CONCLUSION: Based on our findings in this study, it is suggested that initial imaging findings, as listed above, are not a good predictor of response to 90 Y radioembolization. AIM: To evaluate the response to treatment in patients with neuroendocrine tumor liver metastases following yttrium-90 (90Y) radioembolotherapy, as a function of image patterns at presentation for 90 Y radioembolotherapy. METHODS: The study cohort consisted of patients with hepatic metastatic neuroendocrine tumors treated with 90 Y at our institution during a two-year time period. Hepatic metastases were evaluated on a pre treatment study assessing relative arterial enhancement compared to liver, lesion size, necrosis of the lesion, and associated tumor burden in the liver. We used six response criteria: Response Evaluation Criteria in Solid Tumors (RECIST) size, World Health Organization (WHO) size, European Association for the Study of the Liver (EASL) necrosis guidelines, Choi size, Choi necrosis and combination of Choi size and necrosis. RESULTS: About 65 lesions in 17 patients met study criteria and formed the cohort. Statistically significant response was found for lesions <5 cm v s ≥ 5 cm with RECIST (P = 0.04), WHO (P = 0.002) and combined Choi criteria (P = 0.02) % necrosis on the pre-scan had a significant significant response with the Choi necrosis criteria (P = 0.01). There was no statistical significance for the response comparing lesions <2 cm vs ≥ 2 cm or in comparing the degrees of the tumor burden. CONCLUSION: Based on our findings in this study, it is suggested that that initial imaging findings, as listed above, are not a good predictor of response to 90 Y radioembolization.