Focal therapy with irreversible electroporation (IRE)

Focal interventions are becoming increasingly interesting as a treatment option. They allow only the part of the organ affected by the tumour to be treated. The important surrounding structures (e.g. nerves) can therefore be spared.

On a small organ such as the prostate especially, the risk is relatively high of damaging important anatomical surrounding structures which are responsible for the ability of the penis to become erect (potency) and for controlling bladder emptying (urinary continence).

Irreversible electroporation (IRE) uses powerful, locally concentrated electric fields to create tiny openings (pores) in the tumour cell membrane. This destroys the cell.

The aim of IRE is to locally destroy prostate carcinoma – while preserving the rest of the gland and largely protecting the surrounding at-risk structures such as blood vessels and nerves.

Prostate cancer can grow extremely slowly. This is why treatment options range from “active surveillance” for low-risk patients to “radical” surgical removal of the entire gland in high-risk patients. Focal therapy is advised if the status of the carcinoma is somewhere between these two stages.

The criteria are:

  • The patient must be over the age of 18
  • The prostate carcinoma must have been confirmed by histology, must not have spread and there must be no clinically significant parts of the tumour outside the planned treatment area
  • The PSA level must not be higher than 15 ng/ml (9) and the Gleason score (degree of differentiation of tumour cells) must be no more than 3+4 (10).
  • The patient’s life expectancy must be at least ten years.

Other criteria that exclude IRE relate generally to previous treatments or pre-existing conditions.

Beforehand

We admit the patient for two to four days for treatment.

At the start of the treatment, we take ten to twelve tissue cores from various regions of the prostate (biopsies) and analyse them under the microscope. The procedure is controlled via trans-rectal ultrasound, an imaging method that uses ultrasonic waves (6).

If the investigated issue turns out to be cancerous, we then determine the stage of the disease. First we differentiate between local prostatic carcinomas (restricted to the prostate, without any metastases or lymph node involvement and without spread to the area around the prostate) and advanced prostatic carcinomas (with lymph node involvement or other distant metastases, spread to surrounding tissue or to neighbouring organs).

If the carcinoma is local, the laboratory results (prostate-specific antigen, PSA) and the tissue examinations (Gleason score) are then used to decide whether IRE would be appropriate.

During

IRE is carried out under general anaesthetic because the electric current applied can cause disruptive muscle twitching.

The electric fields are applied using thin needles which are introduced through the perineum into the tumour area (Figure 1). The needles are positioned under imaging guidance with constant visual monitoring. To ensure that we are able to proceed with complete precision, our facility uses image guidance involving the combination of MRI images obtained before the treatment with ultrasound images taken during the intervention (MRI-US fusion).

Once the needles have been inserted, treatment begins. The entire procedure takes around one hour.

The remainder of the dead tumour cells are then consumed (phagocyted) by the body’s own immune cells (macrophages) and disposed of.

Figure 1: Image-guided introduction of the IRE electrode through the perineum with the aid of a special template (grid). The entire procedure is carried out under constant image surveillance.

After

After the treatment, patients can go about their normal everyday lives without any restrictions.

After six to eight weeks and then every six months, we recommend an MRI scan of the prostate to check the result of the treatment and to rule out any cell changes in the prostate (lesions).

If the MRI scan is carried out elsewhere, we would be grateful if the image data could be sent to us via CD-ROM for further assessment and quality control. In addition to the MRI scan of the prostate, the success of the ablation should also be checked with the prostate-specific antigen (PSA).

Key structures such as the urethra and nerves are generally not damaged or the damage is only temporary.

This is because IRE protects non-cellular parts of the tissue. Blood and lymphatic vessels as well as the urethra and nerves are also made up of cells from a complex and stable tissue matrix which allows the cells to regenerate after the treatment.

Figure 2: The example shows a prostate carcinoma (arrow) on the right in the peripheral zone of the prostate which has been investigated using different MRI techniques (known as multi-parametric MRI). (a) In the T2 weighting, prostatic carcinoma appears as a “dark” area in the otherwise “lighter” peripheral zone. (b and c) Diffusion-weighted images show limited diffusion (movement) of the water molecules in the area of the tumour, which is due to the high cell density of tumours. (d) The typical rich vascularisation of tumours (hypervascularisation) is recognisable in the contrast-enhanced images in which prostatic carcinoma often lights up.

Figure 3: Visualisation of a prostatic carcinoma in the T2-weighted MRI (left) and corresponding ultrasound image (right). The green ring marks the tumour in both techniques. In the ultrasound, the finding also has a dark border (anechoic in medical jargon).

Contact


Minimally Invasive Tumour Therapy (MITT)
Charité Campus Virchow-Klinikum (CVK)
Department of Radiology
Augustenburger Platz 1
13353 Berlin

  TV report

NanoKnife – Mit 1500 Volt gegen Prostatakrebs
> rbb Praxis, 7.9.2016

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