Kidney Tumour Ablation

Introduction

The purpose of these webpages is to serve as a source of information for patients who may be considering one of the forms of thermal ablation (radiofrequency / microwave ablation or cryotherapy) as a means of treating certain types of renal tumours. It aims to inform the patient about these treatment options and what to expect from the procedures involved.

What is radiofrequency ablation?

Traditionally, cancer has been treated by a combination of surgery, radiotherapy and chemotherapy. Radiofrequency ablation (RFA) involves the use of heat to cause destruction of cancer cells. Small needles are used and inserted into the tumour. The needles are heated and cause thermal damage and eventual destruction of the cancer cells.

The needles used are small, 1-2mm in diameter and therefore no large incision or is required for their insertion. Medical imaging such as a CT or ultrasound scan or a combination of both is used to guide the insertion of the needle. Once the needle is in the correct position, radiofrequency waves are passed through the needle, causing the molecules around the needle tip to vibrate. This imparts heat and friction to the area and kills the diseased tissue. The effect is localised but very frequently and depending on the size of the tumour, the needle is moved to a number of different positions to ensure good coverage of the tumour and its surrounding area.  The dead tissue shrinks away eventually and does not need to be removed by surgery.

What is cryoablation?

Cryoablation (also known more simply as “cryo”) involves the use of ice to freeze tumours.  The ice used is at a temperature of less than -100 ° C and provides a very efficient means of destroying tumour cells in a localised area. It is a method that is able to preserve the normal tissues of the kidney.

Much like RFA, cryoablation involves inserting small needles into the tumour under imaging guidance. The probes used are approximately 1.5mm in diameter. They can either be inserted into the tumour through the skin, which is known as the percutaneous route, or from within the body at the time of surgery. This information webpage will focus on the percutaneous route as offered by some interventional radiologists.

Who is suitable for RFA/Cryotherapy?

Generally, these types of treatment are used for small renal tumours, usually less than 3 to 5cm in diameter. Several other factors will be considered when deciding upon whether or not RFA/cryotherapy is the best treatment option for your tumour. Such factors include the location of the tumour, the surrounding structures close to the tumour, your overall health and age, how well your kidneys are functioning, local expertise and obviously, patient preference. 

The decision to undergo RFA/cryotherapy will be made in conjunction with your referring Doctor (usually a Urologist or Oncologist), the Interventional Radiologist and yourself. You will have had up-to-date imaging, usually in the form of a CT scan, which the Radiologists will look at and base some of their decisions upon and may use to plan any RFA/cryotherapy treatment.

What are the advantages of RFA/cryotherapy?

Generally, RFA/cryotherapy can be performed percutaneously – ie: with the probes being placed directly through the skin and with no need for a large incision. Most procedures can be performed under local anaesthetic with conscious sedation, i.e. with a medication to make you feel sleepy, however for cases and in some institutions general anaesthetic is the preferred option.  There should little in the way of blood loss and as there is no incision, recovery times are much faster when compared to traditional open surgery. 

The techniques can be used as an alternative when a patient is not considered fit enough to undergo surgery. Both techniques can also be re-utilised if required. 

As RFA/cryotherapy are means of local tissue destruction, the damage to the surrounding “normal” kidney tissue can be limited. There is little chance of damaging either the crucial blood vessels or the part of the kidney that collects urine.  These techniques aim to conserve as much as possible of the normal kidney tissue in order to preserve normal kidney function, without the need for dialysis or renal transplantation.

What are the disadvantages of RFA/Cryotherapy?

Both techniques are limited to small tumours, with larger tumours more likely to require surgery. There is also no data about the long-term results of the techniques, but five-year follow-up data is promising with high rates of survival. Also, as with any form of treating cancer, there is a risk of recurrence at the site of the procedure. 

As the techniques require insertion of the needles through the skin, and then into the tumour, some tumours may be inaccessible to the needles without them passing through other vital structures, such as the gut. In these cases, RFA/cryotherapy may not be the most suitable means of treatment.

How is RFA/cryotherapy performed?

The procedure will be carried out either under a general anaesthetic or using sedation. Sedation means that the patient is not unconscious, but is lightly anaesthetised, calm and relaxed.

You will be scanned again routinely as part of the procedure. This allows the Radiologist to further plan the treatment and confirm the best means of access to the tumour. Usually, this is done with you lying on your front or on your side. Using the scans, the point of entry for the needles is marked on the skin. The area of the skin to be used is cleaned with antiseptic solution and local anaesthetic may be used to numb the area involved. A biopsy of the area may be taken prior to the needles being inserted, and then the needles are guided into the tumour, using the CT/Ultrasound images to ensure they are correctly targeted. The ablation is then undertaken, with possibly several areas being targeted and the needles being manipulated several times. A completion scan is then performed to assess the immediate results of the ablation therapy.

The procedure can take up to 2 or 3 hours to complete, depending on the individual patient. If all has gone well, the patient is transferred to a recovery area, and from there, back to the ward.

What are the risks of RFA/cryotherapy?

There is a risk of thermal/freezing damage to structures other than tumour. In most cases, an area of normal-appearing kidney tissue around the tumour will be targeted as it is known that this area may contain microscopic tumour cells that may not be visible on a scan. This reduces the risk of recurrence.  However, other structures adjacent to the kidney may be damaged, such as bowel or blood vessels and cause a bowel perforation or bleeding. Such damage is usually apparent on the post-procedure scan and can be dealt with promptly usually with percutaneous techniques but very occasionally surgery.

With any use of sedation or general anaesthetic, there are some risks involved but all doctors and nurses involved have appropriate training in their use and the actual incidence of such risks are minimal.  For further information about the risks involved in the general anaesthesia you should consult an anesthetist.

There is a risk of an allergic reaction to the dye used when CT scans are obtained. All the staff are trained in dealing with such a situation and medicines used to treat the reaction is kept within the X-ray rooms themselves.

There is a risk of recurrence of the tumour after a RFA/cryotherapy procedure. The exact risk varies from patient to patient and follow-up scans (usually at 3 monthly intervals to begin with) to examine the ablated area will be undertaken.

How do I prepare for RFA/cryotherapy?

Each centre is different, but the following is a brief guide of what to expect from the process.

You should have had an extensive discussion with your Urologist about your kidney tumour, the various treatment options and the risks and benefits of the RFA/cyrotherapy procedure. Having discussed the procedure with your Urologist/ Oncologist, you will be referred to the Interventional Radiologist, and may have had an opportunity to meet them prior to the date of your appointment. An up-to-date CT/MRI/ultrasound scan is vital in planning the route and area that is to be targeted during the procedure. Blood tests will also be carried out, and scans that assess the relative function of one kidney compared to another may be undertaken. 

You will be admitted and given a bed in the hospital for you to recover from the procedure in. You will be given a time for the procedure and will be asked not to eat or drink for 4 hours beforehand. If the procedure is to be carried out under general anaesthetic, a member of the anaesthetic team will meet with you at this stage to discuss what is involved and to assess your suitability.

Upon arriving in the Radiology department, you will be asked to change into a hospital gown, if not already done so. 

Let the radiologist and nursing staff know if you have any major health problems, allergies, or are diabetic. 

The staff involved will ask you to confirm your name and date of birth – don’t be alarmed by this or feel it is a sign of poor organisation; it’s a mandatory requirement that we do this for every case. You will then have the further opportunity to discuss the procedure with the Radiologist carrying out the procedure who will also ask you to sign your consent for the procedure to occur. 

Once this has occurred, you will taken into the room where the procedure is to be performed – usually a CT or ultrasound suite.

What happens after the procedure?

Most patients experience some discomfort following the procedure and this is usually managed by simple analgesia taken in a tablet form. You will be asked to continue the tablets for up to a week.  A fever maybe felt 1 to 2 days following the procedure and there may be a general sensation of “feeling under the weather”. This is usually self limiting and does not represent infection in the treated tumour.  To reduce the risk of infection you will be antibiotics at the time of the procedure. The majority of patients stay and are observed in hospital for one night following the procedure and are then discharged home the following day. Most centres would advise a period of rest for around a week following the procedure with no strenuous exercise, and no driving for a similar period.                       

The needles only make a very small point of entry through the skin and the dressings involved are simple plasters. These can be removed after 48 hours. If there is any  continued bleeding or discharge from the needle sites, you should promptly seek medical advice. 

After you have been discharged, a follow-up consultation with the referring Urologist/Oncologist will be made. Once you see them in clinic, the wounds will be checked and a follow-up scan will be organised.