Ultrasonographic changes in the liver tumors as indicators of adequate tumor coverage with electric field for effective electrochemotherapy

Abstract

BackgroundThe aim of the study was to characterize ultrasonographic (US) findings during and after electrochem-otherapy of liver tumors to determine the actual ablation zone and to verify the coverage of the treated tumor with a sufficiently strong electric field for effective electrochemotherapy.Patients and methodsUS findings from two representative patients that describe immediate and delayed tumor changes after electrochemotherapy of colorectal liver metastases are presented.ResultsThe US findings were interrelated with magnetic resonance imaging (MRI). Electrochemotherapy-treated tumors were exposed to electric pulses based on computational treatment planning. The US findings indicate immediate appearance of hyperechogenic microbubbles along the electrode tracks. Within minutes, the tumors became evenly hyperechogenic, and simultaneously, an oedematous rim was formed presenting as a hypoechogenic formation which persisted for several hours after treatment. The US findings overlapped with computed electric field distribution in the treated tissue, indicating adequate coverage of tumors with sufficiently strong electric field, which may predict an effective treatment outcome.ConclusionsUS provides a tool for assessment of appropriate electrode insertion for intraoperative electrochemo-therapy of liver tumors and assessment of the appropriate coverage of a tumor with a sufficiently strong electric field and can serve as predictor of the response of tumors.

Radiological findings of porcine liver after electrochemotherapy with bleomycin

“…The US findings were dynamic. Hyperechogenic bubbles, which initially form around the electrodes, are a consequence of electrochemical reactions on the electrodes and electrocoagulation of the tissue 27, 29. The liberated gases are chlorine at the anode and hydrogen at the cathode 42, 43.…”

“…Radiologic findings after IRE of hepatic tissue have been thoroughly described and used to determine the area that was irreversibly electroporated22, 23, 24, 25, 26, while there has only been one report of radiologic findings after ECT of liver, where ultrasonographic (US) changes in hepatic tumors were described as indicators of adequate electric field tumor coverage for effective ECT 27. The effect of ECT on healthy hepatic parenchyma and large hepatic vessels has not been previously studied by diagnostic imaging methods.…”

Recent Advances in Electrochemotherapy

“…Therefore, specifically for deep-seated tumors, treatment planning and radiological monitoring during the procedure to determine complete coverage of the treated tumor are of utmost importance. 112,113 Namely, monitoring of changes during and after electrochemotherapy is important for evaluation of the progress of the procedure that is based on pretreatment plan and its results. It is important that tumor is not over treated as this will cause irreversible electroporation, or under treated (not enough cells exposed to electric field above threshold value) as this restricts the access of drugs into the cells and consequently their action on target, that is, DNA.…”

“…It is important that tumor is not over treated as this will cause irreversible electroporation, or under treated (not enough cells exposed to electric field above threshold value) as this restricts the access of drugs into the cells and consequently their action on target, that is, DNA. 112,113 For tumors in the head and neck region, the treatment plan can be coupled to the navigation system for accurate positioning of single long-needle electrodes into and around tumors. 114 Furthermore, the new, sensitive method for the determination of bleomycin in serum and tumors enables a redefinition of the optimal therapeutic window for the application of electric pulses after bleomycin intravenous injection.…”

Ablation of soft tissue tumours by long needle variable electrode-geometry electrochemotherapy: final report from a single-arm, single-centre phase-2 study

“…Admittedly, other variables might have influenced treatment outcome, including distribution of bleomycin and electric current within inhomogeneous tumour tissues 37 , and a discrepancy between pre-treatment plan and actual electrode placement. On this regard, a preliminary experience in patients with liver metastases suggests that US scan holds promise for real-time assessment of the electroporation process 38 , while experimental evidence in animal models indicates that magnetic resonance electrical impedance tomography (MREIT) may be a reliable instrument to predict electric field distribution 39 . Conversely, PET-CT scan performed at one month confirmed the strong antitumour effect of ECT but provided no additional predictive information regarding final treatment outcome; therefore, we believe that a single radiological evaluation may be appropriate to evaluate VEG-ECT response in routine clinical practice.…”