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Prostate Cancer High-intensity Focused Ultrasound
The Future of High-intensity Focused Ultrasound in the
Treatment of Prostate Cancer
a report by
Francois-Joseph Murat,
1,2
Jean-Yves Chapelon
3
and Albert Gelet
2
1. Urology Department, Val d’Ouest Hospital, Ecully; 2. Urology and Transplantation Department, Edouard Herriot Hospital, Hospices Civils de Lyon;
3. French National Institute for Medical Research (INSERM) Unit 556, Lyon
The capacity of high-intensity focused ultrasound (HIFU) in the destruction energy is insignificant. When increasing the intensity of the US waves tissue
of tissue has been known for decades,
1
but unlike imaging systems such damage occurs, which results from two mechanisms: thermal effect and
as ultrasound (US) and magnetic resonance imaging (MRI), its widespread cavitation.
33
Both of these mechanisms will lead to cell destruction by
use has been delayed. Since the 1990s, interest in HIFU has increased with coagulative necrosis.
34
Histologically, a prostate biopsy taken 48 hours after
investigations in a large number of urological diseases.
2–32
Treatment of HIFU shows severe inflammation that hampers the identification of vital PCa
bladder cancers with HIFU has been attempted and prematurely cells. At three months, a prostate biopsy shows the presence of an intense
abandoned.
2
It has been proved to be a promising non-invasive treatment and well-circumscribed fibrotic reaction, allowing easy identification of
for kidney tumours in a few case series
3,4
and there has been a recent residual PCa cells.
18
Therefore, physical processes of cell destruction are
revival of interest in that field.
5
Combined with irradiation, HIFU has also effective almost immediately, which has many clinical consequences.
been used for testicular cancer in a limited series of patients with a solitary
testis.
6
However, the most developed clinical applications are dedicated to First, because induction of apoptosis is not required, late and unexpected
prostate cancer (PCa).
7–32
treatment-induced complications are not observed. To date, bladder or
rectal late toxicities have not been reported with HIFU. Moreover, such side
Physical Principles of High-intensity Focused Ultrasound effects have never been described with HIFU, the opposite of radiation,
The physical principles of HIFU explain most of the advantages of this which is known to induce malignant tissue transformation, and PCa
therapy. To understand the advantages of HIFU versus the other non- radiation therapy, which leads to an increase in long-term secondary
surgical technologies available for PCa, it is important to know how this malignancies.
35
Second, the prostate-specific antigen (PSA) nadir is usually
treatment works. reached three to six months after the procedure, which allows early
feedback on treatment efficacy. This nadir has been demonstrated to be an
HIFU is a thermal therapy that relies on the physical properties of US within independent predictive factor of success for many treatment options for
tissues. Inducing tissue destruction with HIFU requires two conditions: PCa,
36,37
especially for HIFU.
13,22,26
This early biochemical response is a
increasing the energy of the US waves and focusing this energy on a single significant advantage not only for patient follow-up, but also for the early
point. US is a vibration, and when US waves travel through tissue they identification of patients with residual cancer, particularly when considering
deposit energy; however, imaging US is harmless because the deposited that HIFU re-treatment is always feasible and presents a low risk of
complications. Third, no PSA bounces are described, thus allowing a more
convenient and easy follow-up for the urologist and the patient.
Francois-Joseph Murat is a Urology Consultant in the
Urology Department of Val d’Ouest Hospital in Ecully and
the Urology and Transplantation Department of Edouard
With HIFU, not only is the intensity of the US waves increased, but the US
Herriot Hospital in Lyon. He is a member of Dr Albert Gelet’s
waves are also focused. After one HIFU pulse, the focalisation of the
team and has collaborated with him on many clinical high-
US beam will create an extremely small lesion that closely corresponds to
intensity focused ultrasound studies.
the volume of tissue that was previously targeted. The size of the HIFU-
E: gfj-murat@club-internet.fr
induced lesion can be precisely controlled by adjusting the power and the
duration of the US pulse. Moreover, using the bio-heat transfer equation
Jean-Yves Chapelon is Chairman of Research Unit 556 of
HIFU efficacy can be mathematically modelled. This allows the calculation of
the French National Institute for Medical Research (INSERM),
which is dedicated to therapeutic ultrasound research. He
the optimal acoustic intensity necessary to achieve irreversible tissue
participated in the early development of the technical and destruction in a variety of clinical situations, particularly for an irradiated
research projects on high-intensity focused ultrasound.
prostate.
38
Finally, in order to ablate a large volume, such as the entire
prostate, individual HIFU lesions have to be juxtaposed to one another. The
way each lesion is created and the ability to precisely control their formation
and extension have one main consequence: the treated volume is absolutely
Albert Gelet has been Co-Chairman of the Department of
comparable to the targeted volume. With cryotherapy, the lethal
Urology and Transplantation at the Edouard Herriot Hospital
in Lyon since 1980. He became involved early on in the
temperature is reached approximately 3–4mm inside the ice-ball limit, thus
development of high-intensity focused ultrasound (HIFU) requiring the overlapping of any tissue to be ablated by this margin if it is to
treatment, from the first experimental HIFU prototype until
be destroyed; however, with HIFU what has been targeted is treated, no less
its latest version.
and no more. Therefore, no lesions to surrounding organs, such as the
bladder or rectum, are usually observed if the HIFU lesions have been
appropriately and accurately targeted.
32 © TOUCH BRIEFINGS 2008