Predicting treatment response for transarterial embolization in HCC by analyzing intraprocedural parenchymal blood volume
It is difficult to predict which patients with hepatocellular carcinoma (HCC) will have optimal response to transarterial chemoembolization (TACE). While techniques for embolic delivery have evolved over time, identification of tumor factors allowing for quantification of the efficacy of the embolization procedure has not yet been realized. This study evaluated parenchymal blood volume (PBV) before and after embolization as a predictor of angiographic response to TACE of HCC. The authors reasoned that fluoroscopic-cone beam CT could provide semiquantitative assessment of tumoral vascular capacitance through the measurement of PBV. They looked at 40 consecutive patients who had a total of 52 tumors. 33 patients underwent embolization with drug-eluting microspheres, 6 patients underwent conventional chemoembolization, and 1 patient underwent bland embolization. PBV cone-beam CT was performed from the same catheter in the same position before and after embolization. Size measurements were obtained from preprocedural liver CT and tumor response to treatment assessed per mRECIST on posttreatment liver CT performed 3 months after embolization. Embolization was performed to the endpoint of angiographic stasis in all patients. Per mRECIST, 25 tumors (48%) exhibited complete response (CR), 13 (25%) exhibited partial response (PR), 3 (6%) exhibited stable disease (SD), and 11 (21%) exhibited progressive disease (PD). The greatest change in PBV was found in tumors that exhibited CR (200 mL/100 mL ± 99; P = .001) or PR (240 mL/100 mL ± 370; P = .003) to treatment on follow-up imaging. The tumors with lower change in PBVs exhibited SD (64mL/100mL±99;P= .30) or PD (88mL/100mL± 129; P = .06).
This study addresses a vital question. How do we know how well a patient with HCC will respond to transarterial embolization? The authors show that change in PBV correlates to the level of response to treatment as seen on 3 month follow up. While these results may not immediately impact practice pattern or fundamentally change the method of TACE in the near-term, the assesment of dynamic changes in tumor perfusion intraprocedurally may help identify tumors that are unlikely to respond to traditional angiographic endpoints of stasis. Identifying these patients at the time of TACE would indicate which tumors are most likely to benefit from embolization adjuncts (balloon-occlusion delivery, antireflux catheters, etc.). The authors acknowledge limitations, including factors relating to generating and processing PBV maps, artifacts, and generalizability to the larger HCC population. However, this data is important to our understanding of HCC and lays the groundwork for further studies aimed at optimizing both assessment of prognosis and treatment.
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Zagum Bhatti, MD
Department of Radiology, Interventional Radiology Division
University of Texas Health Science Center at Houston, Houston, TX