Dr Kam Juinn Huar, Consultant at the Department of Hepato-pancreato-biliary and Transplant Surgery at Singapore General Hospital explains how ablation therapy can be used to treat liver tumours and liver cancer.
What is ablation therapy?
Ablation therapy is the use of heat or chemical to kill cancer cells. It can be used to treat many types of liver tumours. The two most common types are primary liver cancer (hepatocellular carcinoma), and colorectal liver metastases (colon cancer that has spread to the liver).
Ablation therapy can be facilitated percutaneously without surgery (through the skin overlying the abdomen), or during surgery (open abdominal surgery or minimally invasive surgery, also called keyhole surgery). Typically, a needle probe is guided into a liver tumour by ultrasound or computed tomography (CT).
As far as liver cancers are concerned, surgery remains the best chance of cure. However, ablation therapy can be used to treat cancer that is small. Studies have shown that for tumour less than 3cm, the cure rate is comparable to surgery. In addition to that, it can be the preferred option in the following patients:
- Patients with a few small tumours who are not good candidates for surgery due to poor health or poor liver function
- Patients who are awaiting liver transplant for liver cancer
- Patients who had multiple previous surgeries
- Patients with small but poorly located tumours, or whom surgery may involve removing a large portion of functioning liver together with the tumour
- Adjunct to staged treatment or liver resection for patients with several scattered liver tumours.
- Tumour that have recurred after previous surgery
What are the different types of ablation therapy for liver cancer?
1. Microwave ablation
This is a relatively newer modality. Microwaves are used to heat and destroy cancer cells.
2. Radiofrequency ablation
High-frequency electrical currents are passed through an electrode, which creates heat that destroys cancer cells. The dead tumour cells are gradually replaced by scar tissue over time.
3. Percutaneous ethanol injection (PEI)
Concentrated alcohol is injected directly into the tumour to kill cancer cells.
For larger tumours (3cm to 6cm in diameter), microwave ablation and radiofrequency ablation can be considered, in repeated attempts or in combination with embolization of the blood supply to liver tumour (to starve the tumour’s blood supply).
Most patients who undergo ablation therapy will require 1 to 2 days stay in hospital, which is much shorter compared to surgery. The complications associated with ablation therapy are also less compared to surgery. There is more robust clinical data for radiofrequency ablation and microwave ablation, compared to percutaneous ethanol injection.
How is it done?
Ablation therapy is most often performed by a trained interventional radiologist, or sometimes by a trained surgeon.
Most commonly, the electrode is placed into the liver tumour through a small nick in the skin (a local anaesthetic is used to numb the skin). Intravenous sedation and monitoring of heart rate and blood pressure is performed during the procedure. In some cases, ablation therapy is done with general anaesthesia (GA) in the operation theatre, through open abdominal surgery or minimally invasive laparoscopic surgery.
For larger tumours, there may be a need to reposition the needle electrode into different parts of the liver tumour to ensure adequate ablation. Generally, each ablation takes 10 to 30 minutes. Additional time is needed with multiple ablations and multiple tumours.
Side effects of ablation therapy for liver cancer
Ablation therapy has fewer side effects compared to surgery. The possible side effects include:
- Abdominal pain
- Inflammation of the gallbladder
- Damage to the surrounding organs (diaphragm, bile ducts, bowel) which may require surgical correction, and
- Localized infection or abscess formation at the ablation zone.
Benefits of ablation therapy for liver cancer
Ablation therapy is effective treatment for selected liver cancers (preferably less than 3cm, and up to 6cm) and for selected patients with colorectal liver metastases.It is a relatively quick procedure which involves a short hospital stay.
Serious treatment-related complications are rare. The procedure usually involves minimal discomfort if performed percutaneously (through the skin) or laparoscopically (through minimally invasive surgery).