What is HIFU?
HIFU stands for High Intensity Focused Ultrasound. Using HIFU for the localised destruction of body tissue was established in 1942.
Research into medical applications of ultrasound started in the 50’s, and it was thought that high-intensity ultrasound could be used to treat cancer; however, the absence of methods of imaging prevented this application until the 80’s with the development of the ultra-sound scan. Since then, research on laboratory animals has shown the usefulness of HIFU in the destruction of cancerous tissue. The first patient was treated in 1993 with a prototype of the HIFU apparatus developed in France. In 1996 the first European study, in which several prestigious hospitals participated, was carried out, treating 559 prostate cancer patients with the second prototype of the HIFU apparatus. In recent years the equipment has been enhanced with the addiction of new safety measures. Procedures for treatment have also been optimised.
How does HIFU work?
HIFU works on the same principle as conventional ultrasound. Ultrasound can circulate without producing damage in living tissue, but if the source emitting the ultrasound has enough energy and this is targeted, the temperature on this focus increases to 80ºC, 90ºC or more in 2-3 seconds, which is enough to destroy tissue such as in the prostate. Since ultrasound is non-ionising (in contrast to radiation, which is ionising), the tissue at the point of entry and exit of HIFU is not damaged, and this means that there is no heightened risk after several treatment sessions. The fact that HIFU can kill tissue cells (like, for example, prostate cancer cells) that are not close to the source of the ultrasound makes HIFU a good option for minimally-evasive surgical treatment. Three factors contribute to the destruction tissue: coagulation, cavitation and heat.
The sharp increase in temperature at the focal area (between 85ºC and 100ºC) causes coagulation necrosis. The zone destroyed (the ‘elemental lesion’) with each shot is oval-shaped, measuring 19-22mm in length and 1.7mm at its widest point. Each shot lasts 5 seconds, with a 5-second pause between shots. Prostate cancer treatment is carried out by repeating these lesions, each next to the other, until the whole of the gland has been destroyed. Cavitationresults from the vibration of microscopic gas bubbles (steam) produced within the tissue by successive shots of ultrasound. The sum of the multiple shots in a certain time and space produces a gradual increase in temperature within the organ. This temperature increase is greatest at the centre of the elliptical elemental lesion and spreads outwards. Temperature diffusion is calculated on a computer model requiring the use of safety margins at the level of the apex of the prostate in order to protect the striated sphincter, and if necessary, the neurovascular bundles to preserve sexual potency.
If magnetic resonance (MR) is carried out with a gadolinium injection 48 hours after a HIFU intervention, treated areas can be seen as hypointense areas surrounded a hyperintense ring of 6-8mm. Biopsies taken both from the treated area as well as surrounding ring straight after the HIFU show complete tissue death. Biopsies taken after three months show that dead tissue had been replaced by fibrous tissue.
What equipment is used in HIFU?
There are presently two devices used for HIFU: the Ablatherm®, made in France by EDAP, and the Sonoblate®, manufactured in the USA by Focus Surgery. The Ablatherm has certain advantages over the Sonoblate: lesion length is adjustable, it allows real-time control of the rectal wall, it has multiple safety circuits to avoid accidental focusing on the rectal wall, a detector that interrupts treatment if the patient moves, and integrated 7.5 MHz and 3 MHz ultrasound probes to provide prostate imaging. The applications of the Sonoblate are more limited in that this device only permits treatment of early cases of prostate cancer. The Ablatherm, on the other hand, can be used to treat cases where external radiation has been unsuccessful, or for palliative HIFU. The Sonoblate is used with the patient under general anaesthetic and lying face up, whereas the Ablatherm can be used with a spinal anaesthetic and the patient lying on his side.
The Ablatherm device is made up of two units, interconnected by cables. The control unit is where the urologist sits and from where he operates the computer, and the treatment unit, which consists of the bed on which the patient lies, the endorectal probe, including a completely robotic movement system, and a cooling system (the Ablapak®) – a liquid maintaining temperature in the rectum at 12-14ºC, and which also serves to transmit the ultrasound waves. The endorectal probe is covered with a latex sleeve filled with refrigerating liquid. A computer directs the ultrasound shots to the zones established by the treating urologist. A computer programme provides the urologist with a precise 3-D image of the prostate, and the reconstruction of these images will determine the exact size and position of each lesion making up the treatment, the energy liberated by the HIFU, the location of the endorectal probe and its movement. The automatic positioning of the probe in relation to the rectal wall ensures that prostatic tissue is destroyed up to the capsule independently of a the patient’s anatomy and any small movements he may make.
How is the HIFU performed?
The procedure is carried out either with a general or spinal anaesthetic with the patient lying on his side. The procedure takes 1 to 3 hours depending on prostate size. It is important that the patient does not move during the session. The apparatus (the probe) is placed in the rectum via the anus. The refrigerating liquid inside the sleeve covering the probe ensures the rectal wall is cooled, and the temperature is controlled in real-time.
The procedure begins with the prostate being measured and
a 3 dimensional map being built up of it. After this, the number of shots necessary to complete the treatment is calculated. Lesions to the urethra and sphincter are avoided at prostate apex level. The same precautions are taken laterally, to avoid causing lesions to the neurovascular bundles – damage to these causes erectile dysfunction.
In the standard treatment (for patients with tumours detected early on), after calculating prostate size and the position of lesions, 5-second shots are fired at 4½ second intervals. In the case of patients where radiotherapy has not been successful, the shots last for 4 seconds with 7-second intervals. At the end of the treatment session a vesical catheter is placed and is left in for 2-50 days. If a transurethral resection of the prostate (TURP) or KTP laser treatment is carried out before the HIFU to reduce the prostate volume as much as possible, the time the vesical catheter is left in is 2-3 days. The stay in hospital is less than 24 hours, and the patient is discharged the next day. The catheter is taken out after 3-4 days, but it may be necessary to place another catheter if the patient has problems with urine retention.
The first PSA test is carried out 3 months after treatment. Some centres routinely take a biopsy after 6 months to programme a second session of treatment if there are still malignant cells in the prostate.
HIFU can be used to treat prostate cancer in the following cases:
a – patients with a recently diagnosed localised tumour. (Standard)
b – patients suffering from prostate cancer who have already been treated with HIFU (Re-treatment)
c – patients with tumours where external radiotherapy or radical prostatectomy have been unsuccessful (there is a nodule visible by ultrasound and no metastasis.).
What is the preparation for the HIFU procedure?
The patient should stop taking all anticoagulant medicines 10 days before the procedure and if he takes WARFARIN, this should be suspended at least 5 days before treatment and heparin injected instead. The patient has an enema the day before and the morning of treatment to ensure the bowel is empty. Antibiotics are given intravenously to prevent infections. Before treatment begins, an 18F catheter is placed to empty the bladder and to help to identify the apex of the prostate; this catheter is taken out before treatment.
The patient can eat in the evening after treatment, and is discharged the following morning. There is generally no need for pain-killers.
What patients does HIFU work best for?
a – Patients with a recently diagnosed localised tumour. (Standard).
The standard treatment should be reserved for patients with low-risk (also known as “good prognosis”) tumours, with the following characteristics:
b – patients where external radiotherapy has been unsuccessful
What patients cannot be treated with HIFU?
HIFU cannot be used to treat patients with large calcium deposits in the prostate as this prevents the prostate from being visualised properly and makes controlling the progress of treatment difficult. It is not possible to treat patients who have previously had brachytherapy treatment since the implants in the prostate cause the same limitations to visualisation as the calcium deposits. However, these calcium deposits can be eliminated by TUR. Fibrosis, stenosis, and other problems of the rectum that do not allow the Ablatherm® probe to be placed are also contraindications for HIFU therapy. The same applies to patients with artificial urinary sphincters, or penile, urethral or prostate prostheses. Patients unwilling to suffer loss of sexual activity and take medication to remedy this are also not candidates for HIFU. If rectal wall thickness is greater than 6mm, this is also a contraindication for HIFU. Lastly, patients who cannot lie on their sides for 2-3 hours cannot be treated with HIFU.
What are the results of treating localised prostate cancer with HIFU?
By the end of 2006 more than 12,000 patients had been treated with HIFU in Europe. This treatment has been used with good results in countries such as France and Germany for more than 14 years. Improvements in the HIFU apparatus (Ablatherm®) has led to a great reduction in side-effects and complications.
The results of a study undertaken in 6 European hospitals (3 in France, 2 in Germany and 1 in the Netherlands) was published in 2003. This study followed 402 patients with localised prostate cancer (stages T1-T2). 228 patients had a prostate biopsy 6 weeks after HIFU treatment, 87% of these showing no signs of cancer.
The results of research in Munich were also published in 2003, where 271 patients received HIFU treatment. In 88% of the cases where prostate biopsies were taken, there were no signs of cancer. PSA had fallen to an average of 0.48 µg/L. The disease-free survival rate at 5 years was 66%. If patients are grouped according to initial PSA, disease-free survival rate was 90% if PSA was less than 4 µg/L, 57% if it was 4.1–10 µg/L, and 61% if PSA was 10.1-15 µg/L. These results suggest HIFU offers a high degree of control of localised prostate cancer.
What are the side effects and complications with HIFU treatment?
Up to present there have been no deaths related to HIFU treatment and no patients have needed blood transfusions.
Grade I urine incontinence has been reported in 7% of cases, grade II in 2% of cases, and there have been no reports of grade III urine incontinence. Incontinence improves spontaneously or with the help of physiotherapy for the pelvic floor. Stenosis (narrowing) of the urethra or vesical neck requiring urethral dilations or incisions (internal urethrotomy) has been seen in 6% of cases. The incidence of urgent urination is found in 5-8% of cases, perineal pain in 3%, and urine infections in 2%. Slight or moderate blood in the urine (haematuria) for around 2 weeks is seen in 75% of cases, and this continues for long periods in less than 1% of patients. Perineal pain is greater when sitting, and this is thought to be caused by neuralgia of the internal pudendal nerve; this generally clears up on its own in the first 3-4 months following the HIFU treatment.
Different studies show that 88% of patients treated with HIFU are satisfied with quality of life in respect to urination after the HIFU compared to 63% before the HIFU.
With treatment, prostatic volume increases between 20 and 40%; for this reason it may be necessary to place a vesical or supra-pubic catheter for between 5 days and one month after the HIFU, especially where the patient has not previously had a TUR or KTP laser treatment. Prolonged urine retention is seen in 4% of cases.
Current recommendations advise undergoing a TUR of the prostate or KTP laser photovapourisation of the prostate a month before the HIFU treatment, with which the vesical catheter can be taken out in 3-5 days. In 3-8% of cases, surgery is needed to alleviate urinary obstruction.
Regarding sexual relations, impotence is reported in 60-70% of cases, and retrograde ejaculation in 98%.
The most serious complication with the early prototypes of HIFU was rectourethral fistulas. Currently, with the apparatus used in Europe (Ablatherm®), cases of rectourethral fistulas in patients with localised prostate cancer without previous treatment stand at less than 1%, a figure comparable to that found in patients treated with radical prostatectomy.
What is the future of HIFU?
There is presently a great deal of research going on in this field. The HIFU Urobot is an experimental robotic system which includes a transrectal ultrasound probe and a HIFU transducer. Magnetic resonance images of the patient’s prostate are stored in the computer of the control unit before the operation, and the computer then develops a 3-D model that helps the targeting of treatment on areas where the tumour is present. Enlarged 3-D ultrasound images with contrasting is another of the advances that can be used to improve visualisation of images and the results of the HIFU.
IF YOU HAVE PROSTATE CANCER AND WISH TO BE TREATED WITH HIFU, PLEASE CONTACT US FOR AN APPOINTMENT:
PROSTATE INSTITUTE BARCELONA
Phone number : +34 93 176 76 08