Information for Physicians

Thermal ablation is a minimally invasive image guided method of tissue destruction which is effective for primary and secondary liver or lung tumours, renal cell carcinomas and some soft tissue, adrenal or bone tumours. There are multiple ablation techniques including laser, microwave, cryotherapy or high intensity focussed ultrasound (HIFU), but the current front-runner is RFA, followed by microwave.

A needle electrode/probe or antenna (14 - 17 gauge) with an insulated shaft and an active tip is inserted through the skin and guided into the tumour, using ultrasound or CT imaging. When the needle electrode is in the correct position, the generator can be activated. Radiofrequency uses a rapidly alternating current that causes ionic agitation in the tissue around the tip of the needle, causing friction that heats and kills the diseased tissue. Microwave acts on water molecules causing rapid oscillation that again generates heating. Cryotherapy works by freezing and thawing intracellular water with subsequent disruption of cell membranes. The effect is localized; healthy tissue farther from the needle is not destroyed. Depending on the size of the tumour, the needle may be moved and the process repeated until all of the diseased tissue is destroyed. The dead tissue does not need to be removed surgically - it will shrink and be replaced with scar tissue.

Different centres use slightly different techniques and will tackle different volumes of tumour. We recommend general anaesthesia for liver metastases unless the patient has small volume disease or is unfit for GA. Conscious sedation and LA are usually adequate for simple lung and kidney ablations, more complex treatments require general anaesthesia. We use a combination of US and CT and US-CT co-registration for guidance and monitoring, as each modality has specific advantages. Most patients stay overnight in hospital and are discharged on oral analgesia. Diclofenac is particularly effective in liver capsule pain. Most patients experience some pain or discomfort and many have a low grade fever for a few days. Levels of tumour markers and liver enzymes are often raised after liver ablation.

  • Advantages of thermal abalation
  • 1. Low morbidity
  • 2. It can be used for patients who are not sufficiently fit to undergo surgery.
  • 3. It can be repeated if necessary.
  • 4. It is relatively inexpensive compared to either surgery or many chemotherapy regimes.

Indications vary with the anatomical location and underlying pathology.

Liver Metastases

Current indications include patients with limited but inoperable colorectal or breast metastases. Patients may be inoperable because of the number, location, distribution of liver tumours or co-morbidity. Thermal ablation is much better tolerated than liver resection requiring an overnight stay in hospital and has a much lower associated morbidity and complication rate.

  • Our current guidelines are:
  • solitary metastases smaller than 7 cm
  • as many as 5 tumours < 5 cm
  • as many as 9 tumours < 4 cm.

Other centres operate on different criteria, smaller numbers of tumours, of smaller size but our criteria are based on our survival data. Also by using GA, multiple guidance and monitoring techniques and various adjunctive measures, such as dextrose isolation whereby fluid is injected around the ablation area to provide a buffer and so protect any adjacent vulnerable structures, we are able to treat more aggressively.

Primary Liver Cancer

RFA is indicated where transplantation is not possible or as an interim measure whilst awaiting transplantation. In some centres liver resection is still used instead of RFA but in most centres RFA has become the treatment of choice for small tumours. RFA has superseded percutaneous ethanol injection (PEI) for most HCC. PEI is used where RFA is not possible. Occasionally a combination of RFA and PEI are used for different tumours or different parts of the same tumour.

  • Our recommendation is:
  • solitary tumours smaller than 5 cm
  • as many as 3 tumours < 3 cm
  • in patients with Childs Pugh Class A or B cirrhosis

For larger tumours a combination of chemoembolisation and RFA is better than either technique alone. Where RFA cannot be performed most patients are offered chemoembolisation.

Lung Tumours

Lung RFA is one of the fastest growing areas in ablation particularly the treatment of inoperable pulmonary metastases. RFA is effective in the destruction of small tumours either metastatic or primary. Peripheral tumours are easier to access and carry both a lower complication rate and a reduced chance of recurrence. The optimal relationship of RFA to other therapies has not been established.

Lung Metastases

At the present time it is reasonable to offer RFA to patients with limited numbers < 5 (preferably < 3) of small (< 3.5 cm) inoperable tumours. Larger tumours can be treated in conjunction with radiotherapy or systemic chemotherapy. Most patients have metastatic colorectal cancer but sarcoma, renal, oesophageal/gastric, melanoma, breast metastases have all been successfully treated. Survival analysis in patients with inoperable colorectal lung metastases shows that size is important but the number of metastases, (<10), and whether the metastases are unilateral or bilateral is not. Previous liver resection, liver ablation or concurrent liver ablation does not impact survival as long as all known sites of disease are ablated or resected.

Primary Lung Cancer

Few patients present with stage 1A tumours but ablation is effective and is currently offered to patients who are not operable due to concomitant medical co-morbidity, previous surgery or who present with synchronous or metachronous primary lesions.

Renal Tumours

RFA is a good alternative to nephron-sparing surgery. Current indications include those with multiple renal cell carcinoma (including those with Von Hippel Lindau), contralateral nephrectomy, reduced renal function and those who would not be able to undergo a surgical procedure but could tolerate RFA. Peripheral tumours are more readily and more completely ablated than central tumours. A size limit of 5 cm is usual. RFA has been used successfully to palliate haematuria.


  • General
  • Un-correctable coagulation disorder
  • Focus of active infection
  • For liver ablation
  • Advanced cirrhosis (Child Puch class C)
  • For lung ablation
  • Poor respiratory reserve. The current threshold is an FEV1 of 0.7l or 40% of predicted.

How effective is this form of treatment?

This treatment is very effective for the eradication of small volume tumours. Complete ablation is expected in 90-95% of lung and liver metastases under 3 cm. Definition of the extent of metastases and monitoring of the thermal effect is easier in lung tissue than liver. If there is a nearby blood vessel, recurrence is more likely, but not inevitable. This is because flow in the blood vessel protects the tumour from the heat/cold. If the tumour recurs then further treatment can be given and in this way although the tumour is not eradicated it can be controlled for a period of time.

In patients with secondary colorectal metastases confined to the liver the survival data is better than would be expected without treatment or with only chemotherapy. Our 5 year survival for inoperable patients with colorectal liver metastases who have fewer than 5 tumours < 5 cm in size is 34% from the diagnosis of liver metastases and 24% from thermal ablation. For those with more limited disease, 3 metastases maximal size 3 cm the 5 year survival from ablation is 33%. This compares reasonably well with a 5 year survival of 40% following liver resection for those with operable disease, remember currently ablation patients are those with inoperable disease. In our cohort or patients with secondary colorectal lung metastases with or without ablated liver metastases the 3 year survival is 57%.

For primary hepatocellular carcinoma RFA rivals liver resection but is much less invasive and carries the advantage of being readily repeatable if new foci of HCC develop.

For further information you can contact Dr Alice Gillams by email at

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