With the advent of Interventional Oncology and tumour ablation, patients with renal (kidney) cancer now have access to a range of highly effective minimally invasive treatment options.
Until recently the only treatment options for kidney cancer were active monitoring and / or radical nephrectomy, where the entire kidney is removed. The latest image guided techniques mean that it is now possible to specifically target the tumour and immediate surrounding tissues, without the need to remove the entire organ. This preserves kidney function, reduces surgical risk and gives a quicker recovery time.
Contents
- Introduction to Treating Kidney Cancer
- Advances in Kidney Cancer Treatment
- Kidney Biopsy
- Image Guided Treatments for Kidney Cancer
- Interventional Oncology
- When should Kidney Cancer be Ablated?
- Types of Ablation
- The Benefits of Renal Tumour Ablation
Introduction to Treating Kidney Cancer
The management of kidney tumours has changed dramatically over the last twenty years. Previously, any solid lump discovered in the kidney would either be repeatedly scanned and monitored or removed with the entire kidney – a ‘radical nephrectomy’. As surgical techniques have developed, it has become possible to remove the kidney tumour and only part of the kidney – a ‘partial nephrectomy’ - often performing this surgery through a keyhole method. These advances have allowed for faster recovery and the preservation of the kidney function. However, as the tissues from around the kidney are physically dissected and the kidney cut into there remains a significant risk of bleeding and conversion of the keyhole procedure to an ‘open’ one.
Over the same twenty years, there have also been enormous advances in imaging and alternative methods of tissue destruction that are even less invasive than keyhole surgery.
Advances in Kidney Cancer Treatment
The advances in imaging have had an impact on the detection and treatment of kidney tumours in two ways. Firstly, the number of small kidney tumours detected has risen dramatically. This is because scans themselves are easier to obtain and because the resolution of ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) have improved so much that smaller kidney tumours can now be detected. Often people find themselves diagnosed with a kidney tumour when in fact they had imaging for completely unrelated symptoms.
Secondly, the advances in imaging allow the accurate guidance of needles into tumours and the monitoring of tumour treatment in real time.
The role of Kidney Biopsy
Taking a small sample of tissue is known as a biopsy. This can be performed through a needle that is guided to the target with imaging. As imaging has improved, the accuracy of biopsy has also improved, with a diagnostic sample of tissue obtained over nine times out of ten. Consequently, more patients are undergoing a biopsy of their renal tumour before any treatment takes place to characterise the lump in greater detail, sometimes avoiding the need for any intervention at all if the sample returns a benign tumour.
Image-guided Treatments for Kidney Cancer
In the same way that tissue samples may be obtained by a thin needle inserted through the skin and into a tumour, similar needles may be inserted to deliver energy directly into the tumour to destroy it and a small margin of healthy kidney tissue. This procedure, known as ‘ablation’ refers to any non-radiotherapy form of treatment that destroys tissue focally, while sparing the surrounding healthy tissue. The body then turns the treated tumour naturally into a scar using the immune system.
Interventional Oncology
The decision to proceed with ablation is taken within the context of a multidisciplinary team comprising treating clinican, surgeon and oncologist. Although the treating clinician is often a Radiologist, this field of image guided direct tumour treatment has been termed ‘Interventional Oncology’.
When Should Kidney Cancer be Ablated?
Ablation is suitable in cases where:
- The patient does not wish to undergo surgery
- · The patient is deemed unfit / high risk for surgery
- · There is a solitary kidney or poor renal function
- · There are bilateral tumours or a genetic predisposition to multiple tumours
- · Tumour position would necessitate a radical nephrectomy, but ablation would be technically feasible
Treatment is carried out in a CT scanner within an operating theatre. Tumours up to 4cm may be treated, as long as they do not lie immediately next to important structures within the middle of the kidney.
The patient is given a general anaesthetic and positioned, usually face down, on the treatment bed. The CT scanner is then used to guide the treatment needles into position within the kidney.
Types of Kidney Tumour Ablation
The most common types of energy generated by the treatment needles are cold or heat. Cold-destruction of tumours, or cryoablation, uses compressed argon gas to create ice within the tumour. As the argon expands within the closed tip of the treatment needle, the temperature in the surrounding tissue drops rapidly to around -100 degrees celcius. This ice-ball expands and can be visualised in real time as it covers the tumour and a small rim of normal kidney. After ten minutes of freezing, the ice ball is thawed by the body’s heat, augmented by a short period of heating induced by the use of pressurised helium expanding down the needle. A further freezing cycle follows, as it has been shown that a double freeze/thaw provides the most effective tumour treatment.
Heat destruction of renal tumours is usually in the form of electricity – radio-frequency ablation, or RFA. An alternating current is delivered down an electrode to a grounding pad, usually placed on the thigh. The current induces molecular friction of charged molecules around the needle tip. This friction is translated into heat that is deposited in the surrounding tissues and denatures the cells. Although both methods may effectively kill tumour cells, cryoablation allows the surgeon to watch the treatment taking place in real time. Ice, rather than heat, can be seen on the CT scans as the treatment takes place. Therefore the clinician can be much more certain that the tumour has been covered adequately.
An overnight stay is usually recommended, as although this treatment is usually very well tolerated there is a small risk of bleeding. After discharge, imaging and clinical follow up is suggested at one month, three months and six months after the procedure, and then yearly.
A recent review of the medical literature looking at these types of treatment has shown that there is less chance of local tumour recurrence with cryoablation than with RFA, and this is reflected in the National Institute for Health and Clinical Excellence (NICE) guidelines supporting this treatment. In fact the most recent series published in the medical literature suggest that there is now little difference in long term cancer outcomes between cryoablation and minimally invasive surgery.
Conclusions
The management of kidney tumours is changing. Biopsies are being requested more frequently, in order to confirm a diagnosis of cancer before treatment.
Image-guided cryoablation is very exciting as it offers patients with kidney tumours a genuine alternative from the traditional ‘observation versus surgery’ approach. In particular older patients, or those who would tolerate surgery less well, may find this treatment to be an excellent way of managing an asymptomatic small kidney tumour.
The Benefits of Kidney Tumour Ablation are clear:
- The treatment may be performed with only an overnight stay.
- Being minimally invasive, tumour ablation is very well tolerated.
- Ablation leaves a functioning kidney in place - as the treatment is so targeted.
