Hepatocellular cancer response to radiofrequency tumor ablation: contrast-enhanced ultrasound

Abstract

Radiofrequency ablation (RFA) is increasingly being used as percutaneous treatment of choice for patients with early stage hepatocellular carcinoma (HCC). An accurate assessment of the RFA therapeutic response is of crucial importance, considering that a complete tumor ablation significantly increases patient survival, whereas residual unablated tumor calls for additional treatment. Imaging modalities play a pivotal role in accomplishing this task, but ultrasound (US) is not considered a reliable modality for the evaluation of the real extent of necrosis, even when color/power Doppler techniques are used. Recently, newer microbubble-based US contrast agents used in combination with grey-scale US techniques, which are very sensitive to non-linear behavior of microbubbles, have been introduced. These features have opened new prospects in liver ultrasound and may have a great impact on daily practice, including cost-effective assessment of therapeutic response of percutaneous ablative therapies. Technical evolution of CEUS focusing on findings after RFA are illustrated. These latter are detailed, cross-referenced with the literature and discussed on the basis of our personal experience. Timing of CEUS posttreatment assessment among with advantages and limitations of CEUS are also described with a perspective on further technologic refinement.

Incidence of new foci of hepatocellular carcinoma after radiofrequency ablation: role of multidetector CT

“…Although not statistically significant, this finding may be related to data reported by Park et al concerning a more rapid growth rate of new HCC nodules in patients treated with RFA compared with nontreated HCC, suggesting the need for shorter follow-up intervals in the first group compared with the second [13]. However, it should be noted that the group of patients who did not develop new HCC nodules in our series had a substantially shorter follow-up period, [16,17]. Meno univoci sono i dati riportati in letteratura riguardo i fattori di rischio della recidiva intraepatica a distanza dell'HCC.…”

“…Therefore, all the above confirms the advantage of following up patients treated with RFA with an imaging modality, such as MDCT, which is able to visualise the entire hepatic parenchyma. Other modalities, such as contrast-enhanced US, may be useful for assessing treatment effectiveness - especially during the interventional procedure -but they have few or no indications for detecting new HCC foci during the follow-up [16,17].…”

Ultrasound Imaging of Liver Tumors – Current Clinical Applications

“…CAs increases the procedure's efficiency by a better visualization of the tumor and by correct guidance of the ablation needle in the active (vascularized) area of the tumor (Skjoldbye et al, 2002, Lencioni et al, 2004. After ablative procedures, or even better in one month after the procedure, the absence of the circulation bed in the tumor in arterial phase suggests an effective treatment Vilana et al, 2006, Bartolotta et al, 2008. This principle is also true for chemotherapy with antiangiogenic agents.…”

“…Even under these conditions combination of CEUS with i.v. contrast CT examination is required to detect small metastases between procedures (Bartolotta et al, 2008).…”

Contrast-enhanced ultrasonography used for post-treatment responses evaluation of radiofrequency ablations for hepatocellular carcinoma: a meta-analysis

“…Generally, ablative margin width .5 mm after RFA was considered as safe "disease-free margin". 24 A sufficient safe margin can greatly decrease the local tumour recurrence rate, whereas with the ablative margin width of ,5 mm, secondary RFA should be performed to ensure complete ablation. 22 Among the included studies, only two studies 15,22 have reported the complete ablated rate based on safe margin width.…”