Image-guided microwave ablation of hepatocellular carcinoma (≤5.0 cm): is MR guidance more effective than CT guidance?

Abstract

Background: Given their widespread availability and relatively low cost, percutaneous thermal ablation is commonly performed under the guidance of computed tomography (CT) or ultrasound (US). However, such imaging modalities may be restricted due to insufficient image contrast and limited tumor visibility, which results in imperfect intraoperative treatment or an increased risk of damage to critical anatomical structures. Currently, magnetic resonance (MR) guidance has been proven to be a possible solution to overcome the above shortcomings, as it provides more reliable visualization of the target tumor and allows for multiplanar capabilities, making it the modality of choice. Unfortunately, MR-guided ablation is limited to specialized centers, and the cost is relatively high. Is ablation therapy under MR guidance better than that under CT guidance? This study retrospectively compared the efficacy of CT-guided and MR-guided microwave ablation (MWA) for the treatment of hepatocellular carcinoma (HCC ≤ 5.0 cm).

Methods: In this retrospective study, 47 patients and 54 patients received MWA under the guidance of CT and MR, respectively. The inclusion criteria were a single HCC ≤ 5.0 cm or a maximum of three. The local tumor progression (LTP), overall survival (OS), prognostic factors for local progression, and safety of this technique were assessed.

Results: All procedures were technically successful. The complication rates of the two groups were remarkably different with respect to incidences of liver abscess and pleural effusion (P < 0.05). The mean LTP was 44.264 months in the CT-guided group versus 47.745 months in the MR-guided group of HCC (P = 0.629, log-rank test). The mean OS was 56.772 months in the patients who underwent the CT-guided procedure versus 58.123 months in those who underwent the MR-guided procedure (P = 0.630, log-rank test). Multivariate Cox regression analysis further illustrated that tumor diameter (< 3 cm) and the number of lesions (single) were important factors affecting LTP and OS.

Conclusions: Both CT-guided and MR-guided MWA are comparable therapies for the treatment of HCC (< 5 cm), and there was no difference in survival between the two groups. However, MR-guided MWA could reduce the incidence of complications.

Keywords: Hepatocellular carcinoma; Interventional radiology; Magnetic resonance imaging; Microwave ablation.

Fig. 1

CT imaging before ablation therapy a and after placement of an MWA probe b. Postinterventional CT imaging after removal of the MWA probe shows a non-enhancing ablation zone c. The path of the former probe track can still be seen lateral to the ablation zone. In the center of the ablation zone the formation of bubbles after tissue ablation

Fig. 2

Images of a 58-year-old patient with a small HCC (8.8 mm) in the caudate lobe (a; T1WI dashed circle). First, with the guidance of MR, the probe was accurately inserted into the target lesion to finish the ablation procedure (b, c; T1WI). After the treatment, the thermal-induced damage zone estimated as hyperintensity on the T1 high signal range completely covers the tumor after ablation d. Then, a typical “target sign” is clearly shown in the ablated area of T1WI d, e, and a low point appears in T2WI immediately after MWA f; dashed circle)

Fig. 3

Small HCC in the liver of a 48-year-old man treated with MR-guided MWA. Nodules with a diameter of 12 mm are located in the right lobe of the liver. Before MWA, the nodules have a low signal on T1WI (a; dashed circle) and appear with hyperintensity on T2WI (b; dashed circle). Then, MR was used to proform the puncture path in the T1WI sequence and reconfirm it through the T1WI traverse after reaching the tumor target c. After MWA, a typical “target sign” is clearly shown in the ablated area of T1WI d, f, and a low point appears in T2WI immediately after MWA e

Fig. 4

Flow diagram showing the exclusion criteria. RFA = radiofrequency ablation; LR = liver resection; LT = liver transplantation; TACI = transarterial chemoinfusion; TACE = transarterial chemoembolization

Fig. 5

Kaplan–Meier local tumor progression (LTP) in the CT-guided group versus MR-guided group; a. Mean LTP was 44.264 months (95% CI: 39.484, 49.043) in the CT-guided group versus 47.745 months (95% CI: 43.840, 51.650) in the MR-guided group (P = 0.629, log-rank test). Kaplan–Meier overall survival (OS) of the CT-guided group versus the MR-guided group. b. The mean OS was 56.772 months (95% CI: 53.858, 59.889) in the CT-guided group versus 58.123 months (95% CI: 56.375, 59.889) in the MR-guided group (P = 0.630, log-rank test). The 1-, 3-, and 5-year LTP rates in patients in the CT-guided group were 93.6, 69.5 and 30.7%, respectively, and the 1-, 3- and 5-year OS rates were 100.0, 91.3 and 75.8%, respectively. The 1-, 3-, and 5-year LTP rates in the MR-guided group were 96.3, 81.2% and 28,7%, respectively, and the 1-, 3- and 5-year OS rates were 100.0, 96.2 and 79.4%, respectively