Patients selection
This single center retrospective study was performed in BLINDED and approved by the institutional review board. Informed consent was waived because of the retrospective design. From January 2014 to May 2016 treatment-naïve patients who underwent a first session of cTACE for the treatment of HCC were retrieved from the medical database of our institution. Inclusion criteria were (i) the presence of at least one HCC according to EASL clinical practice guidelines [1], (ii) contrast-enhanced computed tomography (CT) before the cTACE procedure, and during follow-up and (iii) the presence of up to three HCCs to better identify local progression of individual tumors. Tumors that could not be evaluated for response according to mRECIST criteria, (i.e. hypoenhanced on arterial phase and/or infiltrative tumors) were not included in the study.
A total of 86 patients with cirrhosis underwent a first session of cTACE during the study period. Thirty-six patients were excluded for the following reasons: a) more than 3 HCCs, (n = 10); b) systemic treatment before TACE (n = 3: two patients receiving sorafenib and one patients receiving gemcitabine and oxaliplatin); and c) lack of follow-up CT images (n = 11); infiltrative or hypovascular HCC (n = 12).
The final population of this study included 50 patients (mean age 62 ± 12 yo; 45 men [90%]) with 82 HCCs (mean 27 ± 15 mm, (10–75 mm)). Figure 1 shows the patient flow chart.
Conventional TACE procedure
The decision to perform TACE was discussed by a tumor board for each patient (including oncologists, hepatologists, radiologists, interventional radiologists and hepatic surgeons). Before each cTACE session a team of interventional radiologists chose the most appropriate approach for each patient. All cTACE procedures were performed according to recent expert consensus guidelines [14].
All cTACE procedures were performed under local anesthesia by one senior radiologist (with at least 5 years of experience in interventional oncology of the liver). A right femoral approach was obtained with Seldinger technique using a 5F introducer sheath. Digital subtraction angiography or 3-D cone beam CT angiography was used to identify each target lesion and vascular feeders. The celiac trunk or superior mesenteric artery was catheterized using a 5F Cobra or Simmons angiographic catheter. Treatment was performed as selectively as possible with 2.4–2.7-F microcatheters and involved the injection of a mixture of chemotherapy (up to 60 mg of doxorubicin; Adriamycin; Pharmacia Upjohn,) and emulsified poppy seed oil (Lipiodol, Gerbet). Associated embolization was performed by injection of gelatin sponge (Gelitaspon, Gelita Medical B.V.) or polyvinyl alcohol particles (Bead Block, Biocompatibles). cTACE was considered to be selective if the treatment was injected directly into tumor feeders, and as nonselective otherwise.
CT protocol
All pre and post-cTACE contrast-enhanced abdominal CT were performed with a multidetector CT (64-detector LightSpeed VCT; GE Healthcare,). A multiphase acquisition was obtained as follows: after an unenhanced abdominal scan, a nonionic iodinated contrast agent containing 350 mg I mL–1 was administered intravenously through a 16–18 gauge cannula. A mean 2 mL/kg of contrast medium was injected via an antecubital vein at 4 mL/s. No oral contrast medium was used. Arterial, portal, and late venous phase acquisitions were obtained at 35, 80, and 180 s, respectively, following contrast injection. A maximum thickness per slice of 2.5 mm was obtained for each acquisition.
Image analysis and tumor response
Baseline tumor characteristics
Pre- and post-cTACE contrast-enhanced CT images were reviewed by two senior abdominal radiologists (XX and YY with XX and YY years of experience in the field of liver imaging). Images were reviewed in consensus on a picture archiving and communication system (PACS) (Carestream Health). The following items were evaluated and recorded for each treated tumor: a) largest diameter (in mm); b) the presence of a capsule defined as a smooth, uniform, sharp border around the lesion that was clearly thicker or more conspicuous than fibrotic tissue around the background nodules, and visible as an enhancing rim in portal or delayed phase acquisitions; c) the presence of bland portal vein thrombosis; and d) location according to Couinaud’s liver segment classification.
Lipdiodol retention pattern on first follow-up CT
The lipiodol retention pattern was assessed on pre-contrast images of post-TACE CT performed 4 to 6 weeks after treatment (mean 38 ± 9 days; (20–73 days)). To ensure that the entire tumor volume was explored, images were compared with pre-cTACE hepatic arterial phase CT. Lipiodol retention was considered to be complete if the entire nodule volume was hyperattenuating compared to the surrounding liver parenchyma on pre-contrast images (retention could be either homogenous or patchy as long as the whole tumor volume showed lipiodol retention). Lipiodol retention was considered to be incomplete if the nodule volume showed only partial hyperattenuation on post-TACE pre-contrast images. Figure 2 provides schematic examples of the two retention patterns.
Tumor response and local progression
Tumor response was evaluated in a tumor-by-tumor analysis. Tumors were individually classified according to mRECIST [9] as a complete response (CR), partial response (PR), stable disease (SD) or progressive disease (PD). The current study focused on nodules showing a CR, i.e. with no hyperenhanced portions on arterial phase images after cTACE. Therefore, patients without a CR in tumors on first follow-up CT were excluded from the local progression analysis, because a second cTACE session was required [15].
Each tumor was followed until local progression occurred (follow-up CT was performed every 3 months in patients), which was defined as the appearance of a hyperenhanced nodular portion with washout on portal or delayed phase images (Fig. 3), within two cm from the treated lesion. In case of doubt of local progression, hepatic MR imaging was performed. The time from cTACE to local progression was recorded. If a tumor showed no local progression on the last available follow-up CT (at least 6 months after TACE), the nodule was considered to be a persisting CR (Fig. 4).
Statistical analysis
Data were expressed as means, standard deviations and ranges, or number of cases and frequencies, as appropriate. A Fisher exact test or a Chi-2 test was used to compare frequencies. The Student t test or Mann-Whitney test was used to compare continuous variables according to data distribution. The clinical, tumor and technical characteristics of the lipiodol retention pattern were identified by univariate analysis, and significant factors (p < 0.1) were entered into a binary logistic regression model. Association between lipiodol retention pattern and local progression was also weighted by means of odds ratio (OR). Time to local progression was defined as the time between the cTACE session and the first local progression. Factors associated with local progression were identified by a Cox-Mantel model, and provided with the corresponding hazard ratios. A p value < 0.05 was considered to be significant. All analyses were performed with the Statistical Package for the Social Sciences software, version 20.0 (SPSS Inc.)