Fateh Ahmad

Liver ablation techniques: a review

BackgroundAblation techniques for unresectable liver carcinomas have evolved immensely since their introduction. Results of studies involving these techniques are restricted to reports of patient case series, which are often not presented in a standardised manner. This review aims to summarise the major studies in ablation technologies and present them in a way that may make comparison between the major modalities easier.MethodsAll major databases (Medline, Cochrane, Embase and Pubmed) were searched for studies using microwave, radiofrequency or cryoablation to treat unresectable liver tumours. Only studies with at least 30 patients and 3-year follow-up were included. Complication, recurrence and survival rates of all studies are summarised and presented.Results and conclusionIt is difficult to compare ablation modalities, as probe design and energy sources have evolved rapidly over the last decade. Ablation offers an invaluable palliative option and in some cases it may offer rates of cure approaching that of surgical resection with lower morbidity and mortality. Perhaps the time has come, therefore, for prospective large-scale randomised control trials to take place comparing ablation modalities to each other and surgical resection.

Microwave ablation for unresectable hepatic tumours: clinical results using a novel microwave probe and generator.

BACKGROUND Microwave ablation is an in situ method of tumour destruction used to treat patients with unresectable liver tumours. A new microwave generator and probe, designed to deliver high energy into solid tumours quickly has been developed at our institution. We report the results of its use in patients with unresectable liver tumours treated by a single surgeon in a single institution. METHODS Thirty-one patients with 89 unresectable liver tumours were recruited into the study and underwent microwave ablation in a single procedure. RESULTS There were no post-operative complications. At a median of 24 months post ablation, 15 patients were alive with 7 patients disease free. At a median of 26 months, 8 patients were alive with tumour recurrence but only 1 with local recurrence. The remaining 7 patients with recurrence were found to have new disease at locations remote from the ablation site. Fourteen patients died of disease progression at a median survival of 15 months, with only 1 patient with local and remote tumour recurrence. Of the total numbers of tumours treated (n=89), a local tumour recurrence rate of 2% was observed. Overall median survival was 29 months with 3 year survival of 40%. DISCUSSION Microwave tissue ablation using this novel generator and probe has a low local recurrence and complication rate. Overall survival is comparable to alternative ablation modalities and its ability to treat, even large tumours, with a single insertion of the probe makes it an extremely attractive treatment option.

Changes in interleukin-1β and 6 after hepatic microwave tissue ablation compared with radiofrequency, cryotherapy and surgical resections.

BACKGROUND Cytokine changes after microwave tissue ablation (MTA) were compared with hepatic resection, cryotherapy (CRYO), and radiofrequency ablation (RFA). Cytokine production was measured at various ablation volumes for each modality and correlated with the transitional inflammatory zone produced by the ablation techniques. METHODS Live rats underwent MTA, surgical resection, CRYO or RFA of 15%, 33%, or 66% of the total hepatic volume. Serum samples were collected preoperatively and at 1, 3, 6, 24, and 48 hours after surgery and analyzed for pro-inflammatory cytokines interleukin (IL)-1β and IL-6. RESULTS Significantly higher levels of both cytokines were present after CRYO and RFA compared with MTA, hepatic resection, or controls (P < .001). All animals survived except those undergoing RFA or CRYO of 66% of the hepatic volume, which died within 6 hours. Transitional zones produced after RFA were larger than those after CRYO or MTA, but no correlation was present with the amount of cytokines. CONCLUSIONS Large-volume MTA is associated with a significant decreased cytokine response and is well tolerated compared with RFA and CRYO.

Heat Shock Protein 70 Expression Following Hepatic Radiofrequency Ablation is Affected by Adjacent Vasculature

BACKGROUND Heat shock proteins are a highly conserved family of stress response proteins. Members of the heat shock protein 70 (Hsp70) family prevent protein misfolding and aggregation. Following radiofrequency ablation of unresectable liver tumors an interface appears between the irreversibly damaged and normal liver. The fate of this transition zone is critical and is believed to be responsible for local recurrences. Hsp70 is expressed in response to thermal stress and may influence the fate of cells in this transitional zone. It is also recognized that the presence of large vessels or a perivascular location of tumors also influences the recurrence rate. The aim of this study is to examine the transition zone and observe the effect of local blood flow on ablation morphology and Hsp70 expression. METHODS Radiofrequency ablation was performed in 25 rats at various distances from the liver hilum. Tissue was retrieved and analysed at time points 0, 4, 24, 48 h, and 2 wk following treatment. Tissue was analyzed histologically with hematoxylin and eosin staining (H and E,) and immunohistochemically for Hsp70 expression. RESULTS All rats survived the procedure. H and E staining revealed previously unreported foci of apoptosis at the ablation edge and deep in the normal hepatic parenchyma. Hsp70 was expressed in the transition zone at 4 h and peaked at 24 h. The degree of Hsp70 expression was significantly influenced by the distance from surrounding vasculature. CONCLUSIONS This study reports several previously unreported findings. There is increased apoptosis distal to the ablated zone suggests leakage of radiofrequency (RF) current down blood vessels originating in the ablation zone. The degree of Hsp70 expression in the transition zone correlates with time after treatment and the size and location of any adjacent vasculature. These findings suggest that heat shock proteins may play a role in the ability of damaged cells to recover and survive at the periphery of an ablation zone.

Renal effects of microwave ablation compared with radiofrequency, cryotherapy and surgical resection at different volumes of the liver treated

Background: Renal changes after microwave tissue ablation (MTA) were compared with those following hepatic resection, cryotherapy (CRYO), and radiofrequency ablation (RFA). Structural damage producing renal impairment has been assessed directly by examining tissue specimens and by serum analysis for two sensitive biomarkers, retinol binding protein (RBP) and the heat shock protein 70 (HSP‐70) for each modality at different ablation volumes.

Cryotherapy of the liver: a histological review.

INTRODUCTION Cryotherapy has been largely used in the past for palliation of unresectable liver tumors, but high local recurrence rates and peculiar systemic complications have determined its progressive abandonment. This review analyzes the histological changes produced to provide the basis for the local recurrences. MATERIALS AND METHODS A detailed literature search was performed on studies focusing on liver cryotherapy. Included were only those that described the histological characteristics in detail. RESULTS A total of 22 studies were found, one clinical and the others in-vivo animal studies. Similar to other ablative techniques, cryotherapy produces a lesion which is composed by a central zone of coagulative necrosis surrounded with a transitional inflammatory zone. The lesions dimensions and morphology are influenced by numerous factors including the probe temperature, diameter, the duration of freezing time, fast cooling rate, slow thawing rate, the number of freezing cycles and the inflow occlusion (Pringle maneuver). The temporal evolution is consistent across studies and leads to a progressive inflammatory invasion of the necrosis with definitive fibrotic substitution. CONCLUSIONS Lesions obtained after cryotherapy seem similar and behave as those obtained after other techniques of liver ablation. However, controversial areas still exist and include the optimum number of freeze thaw cycles, the place of inflow occlusion, the potential corrupting effects of intra-lesional or proximal blood vessels on ablation morphology. The influence of these factors on the local recurrences are still not fully understood.

Large Volume Hepatic Microwave Ablation Elicits Fewer Pulmonary Changes than Radiofrequency or Cryotherapy

BackgroundLung changes after microwave tissue ablation (MTA) of different volumes of liver were compared with hepatic resection, cryotherapy (CRYO) and radiofrequency ablation (RFA).MethodsLive rats underwent MTA, surgical resection, CRYO or RFA of 15%, 33% and 66% of total hepatic volume and lung samples were collected at the time of death. Lung impairment was assessed directly by examining the tissue specimens for the degree of interstitial pneumonia and by comparing the alveolar thickness in the different groups.ResultsAll RFA and CRYO rats undergoing 66% of ablations died, but the MTA group had no fatalities. Following 66% RFA or CRYO ablations, the animals had a significantly increased thickness of the alveolar septa compared to 15% or 33% ablations and to 66% ablations in the MTA group.ConclusionsLarge volume MTA is associated with a significant reduction in consequent lung damage and is well tolerated compared to RFA and CRYO.