Percutaneous liver tumor ablation

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Percutaneous liver tumor ablation techniques are well-established and effective therapeutic alternatives for the treatment of primary and secondary liver tumors. Hepatocellular carcinoma (HCC) and colorectal oligometastatic disease are the most common indications. There are specific indications and contraindications, but the techniques are mostly limited to small oligonodular and favourably-located lesions.

They potentially include both thermal (radiofrequency ablation (RFA), microwave ablation (MWA), and cryoablation) and non-thermal ablation methods (irreversible electroporation (IRE)).

Indications

  • HCC: the Barcelona clinic liver cancer (BCLC) group recommendations have been widely adopted for HCC treatment decision and percutaneous ablation is recommended, as an alternative to surgery, for:
    • stage 0 (performance status 0 and Child-Pugh score A) - very early stage: single liver lesion measuring <2 cm 
    • stage A (performance status 0-2 and Child-Pugh score A-C) - early stage: solitary lesion >2 cm or early multifocal disease characterized by up to 3 lesions measuring less than 3 cm
  • liver metastasis: when a patient is not a candidate for surgical resection or has failed other therapies . As per an international consensus in 2015
    • lesion size: <3 cm, but with allowance to <5 cm well-located lesions (defined as those with easy access)
    • number of lesions: five or fewer tumors should routinely be considered for ablation. The consensus opens margins to up to nine lesions in selected cases
  • benign liver lesions: selected application of percutaneous ablation for the treatment of benign liver lesions (e.g. hemangiomas and hepatic adenomas) has been performed
    • prevent hemorrhage
    • potential malignant degeneration (adenomas)

Contraindications

  • general
    • uncorrectable bleeding diathesis (abnormal coagulation indices)
    • active infection
    • poor patient performance status (ECOG >3)
    • Child-Pugh score C
  • radiofrequency ablation (RFA) / microwave ablation (MWA)
    • tumor involving major hepatic bile ducts
    • proximity to vital structures such as a major vessel or adjacent organs (e.g. colon) - relative contraindication

Procedure

Preprocedural evaluation
  • recent CT or MRI liver is required for planning
  • challenging locations not necessarily preclude the procedure
    • at the hepatic dome abutting the diaphragm
    • close to the hepatic hilum
      • potential risk of damaging major bile ducts or central vessels 
    • at a subcapsular location
      • pain at the liver capsule  
  • no evidence supporting antibiotic prophylaxis 
Technique
  • sedation
    • general anesthesia is not mandatory 
    • anesthesiology care is advised 
  • artificial ascites or fluid dissection 
    • RFA: dextrose 5% is preferred with saline contra-indicated 
    • MWA: any type of fluid 
  • gas dissection with CO2 is an alternative to fluid 
Postprocedural care
  • imaging follow-up to assess treatment success is recommended with either multiphase CT liver or MRI liver
    • the first scan one month after treatment
      • most perfusion abnormalities tend to vanish within a month of the procedure
      • note that faint enhancement surrounding the ablation zone may be seen and is related to treatment-induced inflammatory reaction and granulation tissue. They tend to vanish within 6 months after treatment
      • eventual gas bubbles related to necrotic tumor tend to disappear within several days
    • then three months intervals

Complications

  • reported post-ablation self-limiting symptoms include
    • nausea and vomiting 
    • loss of appetite
    • fever 
    • abdominal pain 
  • post-procedural complications include
    • liver abscess
    • bowel perforation
    • pneumothorax
    • intraperitoneal bleeding 
  • procedural mortality is low 

Outcomes

  • incomplete ablation: the presence of residual tumor post-treatment, usually picked on the first imaging follow-up
  • complete ablation
    • HCC: non-vascular ablation zone on the follow-up scan
    • metastasis: non-vascular ablation zone covering the target with a good surrounding margin