Background. Electrochemotherapy is a new local treatment method for liver tumours. The first clinical studies on the use of electrochemotherapy with bleomycin for treatment of hepatocellular carcinoma and colorectal liver metastases have been published. Included patients had unresectable tumours, which were also not eligible for other local treatments, e.g. radiofrequency and microwave ablation. The authors of these pilot studies reported that electrochemotherapy with bleomycin is feasible, safe and effective for liver tumour treatment. However, when histopathological examination of liver biopsy specimens was performed, damage to normal small-calibre blood vessels was observed. Inadvertent damage to major blood vessels and bile ducts of the liver during treatment could cause serious harm to patients. Therefore, more data on the effects of electrochemotherapy with bleomycin on normal liver parenchyma, blood vessels and bile ducts is needed to ensure safe treatment.
Aim and hypothesis. Our aim was to comprehensively evaluate acute histological, radiological and biochemical changes in normal porcine liver parenchyma after electrochemotherapy with bleomycin. We placed additional emphasis on electrochemotherapy induced changes in major liver blood vessels and bile ducts. Our hypothesis was that the use of electrochemotherapy with bleomycin near major liver blood vessels and bile ducts does not cause clinically important changes which could lead to organ failure and other serious complications.
Methods. Permission for carrying out the experiments was obtained from the Ethical Commission for Animal Experimentation at the Administration of the Republic of Slovenia for Food Safety, Veterinary and Plant Protection. All procedures were compliant with national and European legislation. We tested our hypothesis by designing a translational animal model study which we carried out on eight female domestic pigs. We chose domestic pigs as our experimental animals, as their liver is very similar to human liver. To assess acute liver parenchyma changes, we performed electrochemotherapy with bleomycin in six test pigs and additionally applied electric pulses only in two control pigs during open surgery. In each test animal, electric pulses were applied in four different anatomical locations in the liver, for a total of 32 applications. Immediately after the procedure we assessed the livers with the use of contrast-enhanced computed tomography. Two or seven days after surgery, the pigs were euthanized, and their livers explanted for histological examination. Blood samples were collected before surgery and before anaesthesia for laboratory analysis. We also looked for development of possible clinical signs of liver failure. We presented the histological and radiological findings descriptively, while we compared the results of blood sample testing using paired t-sample testing.
Results. We found that electrochemotherapy with bleomycin caused limited damage to normal liver tissue adjacent to the electrodes. No changes were observed in the liver parenchyma farther than three mm away from the electrodes. The most important finding of our study is that despite the risky use of electrochemotherapy with bleomycin, no thrombosis or other important changes in major liver blood vessels and bile ducts were observed. We observed variable levels of damage to the small blood vessels adjacent to the electrodes, from partial damage to complete necrosis. The observed changes in the liver were identical when electrochemotherapy with bleomycin or electrical pulses only were used, thus confirming that the changes were caused by the application of electrical pulses, with bleomycin causing no further damage to the liver. No clinical or biochemical signs of liver failure or systemic inflammatory response were observed in the experimental animals. Seven days after the procedure we already saw regenerative changes in the liver, therefore we consider the probability of development of further clinically important changes to be minimal.
Conclusions. Electrochemotherapy with bleomycin does not cause clinically important changes in normal liver parenchyma. Our study confirms its safety for use in treatment of patients with liver tumours near major blood vessels and bile ducts.
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