Can we use Functional Liver imaging for evaluation of post radiation toxicity from Y90 and SBRT therapies

127 Introduction: Can we use Functional Liver imaging for evaluation of post radiation toxicity from Y90 and SBRT therapies ? A key concept, when facing similar efficacy, in selecting the most appropriate therapeutic option between two competing treatments, such as Radio-embolization (Y90) and external beam radiation (SBRT) for Liver Cancer is understanding the personalized specific toxicity of each modality. This is further emphasized in the setting of chronic liver disease where the competing morbidities and mortalities of liver failure, liver cancer and treatment induced accelerated liver failure may overlap. Therefore we need better tools to assess the toxicity of these treatments. One of the few tools that has the potential to answer these questions, is the Functional HIDA liver scan by quantifying functional changes in both global and regional Liver function before and after treatment. This has showed promise for safer selection of patients for liver surgery. We wanted to see how the study performs for these two radiation based treatments. Over a 2 year period we collected pilot data on these two therapies. Methods: We enrolled 28 pts treated with SBRT and 15 pts treated with Y90. Functional HIDA scans were performed before and after therapy, for the SBRT group theses were acquired 3 and 6 months post treatment of for the Y90 group only 3 months. Dynamic Planar images were acquired for 6 minutes post injection, thereafter SPECT images were collected and processed. Only 22 pts had pre and post data sets, with poor compliance from the Y90 group. However the Y90 group had more advanced liver disease and liver cancers. Results: Y90 assessment was complicated due to advanced liver disease and advanced liver cancers - however pts with low liver function tolerated procedures better than expected when compared to resection -pts with low extraction fractions <3 did not go into immediate liver failiure and seemed relatively radio resistant. Others showed typical 50% losses in liver function and tolerated well from 8.4 to 4.4 and 8.6-4.9. For SBRT, usually pts had less severe liver disease and smaller single tumors, again pts with low liver function tolerated the therapy better than expected as compared to liver resection, with 5 pts with extraction less than 3% per minute doing well. Overall average liver function was 5.2% with a very minimal average 25% reduction in function post therapy suggesting very low toxicity. Conclusions: Overall SBRT and Y90 appear to have lower thresholds of liver function for safe therapy as opposed to surgery. SBRT shows little 3 month toxicity and therefore perhaps may be used in pts with poorer functioning livers and larger lesions than is accepted today. Due to the complexities of poor liver function and advanced liver cancers it is harder to reach early conclusions concerning the toxicity of Y90 with need for larger studies with many more patients. But preliminarily post y90 functional imaging has shown complete loss of function in areas treated which is important for future treatment planning. In patients with borderline liver function, better understanding the pre-treatment risk of toxicity is important.