Information for Physicians
RFA 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 or bone tumours. There are multiple ablation techniques including laser, microwave or high intensity focussed ultrasound (HIFU), all produce coagulation necrosis but the current front-runner is RFA.
A needle electrode (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 and the radiofrequency waves produce vibration of the molecules in the tissue around the tip of the needle, causing friction that heats and kills the diseased tissue. That effect is localized; healthy tissue farther from the needle electrode is not destroyed. Depending on the size of the tumour, the needle electrode 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 use 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 lung and kidney ablation. We use a combination of US and CT for guidance and monitoring, as each modality has specific advantages. We are currently investigating US-CT co-registration software. 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 RFA
- 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. RFA is much better tolerated than liver resection requiring an overnight stay in hospital and has a much lower associated morbidity and complication rate.
- At Middlesex-UCH we would consider patients with:
- solitary metastases smaller than 7 cm
- as many as 5 tumours < 5 cm
- as many as 9 tumours < 4 cm.
Other centres operate on more restrictive 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 dextrose isolation 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. 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.
- At Middlesex-UCH we would consider patients with Childs Pugh Class A or B cirrhosis with:
- solitary tumours smaller than 5 cm
- as many as 3 tumours < 3 cm
For larger tumours a combination of chemoembolisation and RFA may be appropriate. 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. At UCH alone we have performed over 40 lung treatments in the last year. 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. 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.
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.
Contraindications
- 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 of an FEV1 < 1.0 may be revised downwards with greater experience.
How effective is this form of treatment?
Tumours can recur at the site of a treatment and this occurs in 33 - 40%. Tumours are more likely to grow back if there is a nearby blood vessel as flow in the blood vessel protects the tumour from the heat. 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 29% from the diagnosis of liver metastases and 26% from first thermal ablation. This compares reasonably well with a 5 year survival of 40% following liver resection but in operable candidates.
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.
Ongoing trials
- 1. Microwave vs. RFA
- We are investigating a new percutaneous microwave device in a randomised comparison of RFA and microwave in patients with multiple liver tumours either primary or secondary. Microwave devices have been available for use at open surgery but only recently has a smaller version become available for minimally invasive treatment through small skin punctures. Initial experience with microwave suggests it is able to heat tumours faster and this means more extensive ablations can be performed.
- 2. CT and US Co-registration
- New software which allows the real-time US image to be matched up or co-registered with high definition CT images. This facilitates the placement of needle electrodes into tumours even when they are difficult to see on the ultrasound scan.
- 3. CT Monitoring of Lung Ablation
- Evaluation of the efficacy and the predictive value of CT imaging following on from lung ablation.
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If you want to refer a patient for RFA?
Write to Prof Lees or Dr Gillams at:
- Specialist Xray
- Podium 2
- University College Hospital
- 235 Euston Road
- London, NW1 2BU
- Please include any recent CT or MRI scans.
For further information you can contact Dr Alice Gillams by email at a.gillams@medphys.ucl.ac.uk.