04:21 PM Abstract No. 121 Quantitative and qualitative 99mTc MAA SPECT/CT imaging predicts response to therapy for patients treated with Yttrium-90 (90Y) radioembolization

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Selective 90Y radioembolization therapy for hepatic malignancies involves planning angiography and 99mTc macroaggregated albumin scintigraphy (99mTc -MAA) to assess lung shunt fraction and extrahepatic perfusion. The purpose of this study is to assess the relationship between tumor MAA uptake by SPECT/CT and response following radioembolization. 22 patients with primary hepatic malignancies (non-colorectal) or hepatic colorectal metastases underwent 99mTc -MAA hepatic artery perfusion with SPECT/CT. Qualitative evaluation and quantitative evaluation with tumor to disease free liver parenchyma background ratios (TBR) of SPECT were correlated with CT response. Post-radioembolization Bremsstrahlung SPECT imaging was also performed to assess for similar correlations. The mean MAA tumor TBR in the patients that did not progress was 11.0 ±13.8 (n=14), significantly higher than the TBR of patients that progressed (2.7±1.3 (n=8) (P<0.05). The pattern of 99mTc -MAA distribution was predictive of therapy response. In all cases, intense homogeneous uptake was seen in patients who responded; absent uptake was seen in those who progressed. Uptake on post-radioembolization Bremsstrahlung SPECT did not correlate with response. Our findings suggest that the pattern of uptake on planning 99mTc -MAA imaging can predict response to subsequent radioembolization. Bremsstrahlung SPECT imaging, which is not typically performed, did not correlate with response. Evaluation of 99mTc -MAA uptake on routine pre-therapy studies could potentially serve as a critical decision node in the pre-treatment assessment of patients for radioembolization. Such analysis would extend the utility of this routine study beyond a simple assessment for extrahepatic perfusion, thereby leveraging information inherent to the scan.