Abstract No. 329 - Patterns of necrosis following transarterial chemoembolization (TACE) and correlation with mRECIST outcomes

Abstract

No. 329 Patterns of necrosis following transarterial chemoembolization (TACE) and correlation with mRECIST outcomes P. Guniganti, G. Gonzalez, K. Fowler, N.E. Saad, N. Vachharajani, W. Chapman; Mallinckrodt Institute of Radiology, St Louis, MO; Transplant Surgery, Washington University, St Louis, MO Purpose: Objective response rates based on standard RECIST metrics are inadequate for determining treatment response. As a result, modified Response Evaluation Criteria in Solid Tumors (mRECIST) have been adopted for hepatocellular (HCC) clinical research. Application of these criteria may be challenging in clinical practice depending on the pattern of tumor necrosis. Specifically, measuring the largest dimension of enhancement is challenging when there is patchy or central necrosis. The purpose of this study was to evaluate the different patterns of necrosis seen on imaging studies following TACE and compare these results with explant pathology. Understanding patterns of necrosis may help guide efforts to improve TACE response assessment. Materials and Methods: Patients were included in the study if they underwent TACE for HCC and had preand posttreatment contrast enhanced magnetic resonance imaging available for review from 2006-2012. Index lesions were identified on preTACE imaging and defined as the largest lesion meeting criteria for HCC. Patterns of necrosis were evaluated in the post contrast arterial phase and characterized as central, heterogeneous, diffuse, or peripheral. These patterns were then compared with mRECIST classification on most recent imaging and explant pathology. Results: 429 patients underwent TACE between 4/11/2006 and 8/26/2013. Of these, 99 patients underwent transplant for HCC. On preliminary analysis, 36% of patients showed complete response, 43% showed partial response, and 21% showed no response. Of the patients with partial response: 58% showed central necrosis with peripheral nodular enhancement. 33% showed peripheral necrosis with central enhancement. 8% showed patchy enhancement. Patients with no initial response were evaluated after a second TACE procedure: 50% showed complete reponse. 33% showed central necrosis with peripheral nodular enhancement. 17% showed patchy necrosis. Conclusion: Determining treatment response and need for repeat treatment is essential. While mRECIST is clearly an improvement beyond RECIST, it is difficult to apply in the setting of patchy or central necrosis, which was seen in 66% of patients with partial response of the index lesion.