Magnetic resonance imaging (MRI)-guided ultrasound therapy could be an effective way to treat women with uterine fibroids, improving their quality of life and avoiding hysterectomy, as many recent studies have shown (REST and EMMY).
Speaking at the Global Embolization Symposium and Technologies (GEST) meeting, Dr Wladyslaw Gedroyc, St Mary's Hospital and the Imperial College School of Medicine, London, UK, illustrated the great potential of this technique, as well as discussing other possible uses for the technology in different areas.
Firstly, Gedroyc explained that focused ultrasound (FUS) uses ultrasonic power approximately 5000 to 10,000 times that of diagnostic ultrasound; produces intense local heating at focus which is relatively small; does not require intervention; and can be guided by magnetic resonance (MR) to target and controlled with online MR thermal map (Figure 1).
Gedroyc then clarified that MR guided focused ultrasound (MRgFUS) eg. ExAbate, InSightec, combines two systems:
1. MRI scanner to visualise patient anatomy, map the volume of tissue to be treated, and control the treatment by monitoring the temperature of the tissue after heating.
2. Focused beam of ultrasound energy that heats and destroys the tissue using high-intensity sound waves.
According to Gedroyc, "This is the first time the two systems have been combined in one product and the first time MR has been used to monitor tissue temperature."
MR guidance also provides the following:
• 3D anatomic information for exact tumour targeting
• Beam path visualisation for safe treatment
• Real time temperature feedback to control treatment
• Immediate treatment outcome assessment.
Gedroyc explained, "The most common treatment modality is actually 'wait and see' approach - only when the symptoms become almost unbearable is the patient directed to treatment - most often hysterectomy."
The historical treatments of uterine fibroids are:
• Surgery, hysterectomy and myomectomy
• Embolisation
• Laparoscopic approaches
With this technique, the FUS destroys the fibroid tissue and the whole process is very safe with very few side effects. The procedure is completely non-invasive and can be done as an outpatient procedure. Once the patient is positioned on the FUS device (see Figure 2), the FUS waves heats the target area (up to 85°C) and destroys the tissue. MRI provides mapping of the lesion and thermal feedback during the procedure. Following completion of the treatment, MR contrast can be administered and imaging performed to evaluate changes in tissue perfusion. This imaging provides an indication as to what part of the tumour was affected by the treatment, said Gedroyc (Figure 3).
FUS studies so far: Safety
Gedroyc then discussed studies that have been carried out using FUS so far. In terms of safety, such studies have:
• Included patients booked for hysterectomy who had FUS treatment prior to surgery
• Reported no damage to adjacent tissues
• Demonstrated that imaging targeting correlated with site of pathology damage very well
Efficacy
The effectiveness of FUS studies included the following points:
• FDA regulated
• Two groups treated prospectively and assessed similarly: 1. FUS treatment, 2. hysterectomy
• FUS group treated and assessed with UFS-QOL (Uterine Fibroid Symptom and Quality of Life) questionnaire, SF36 (health survey) and MR volume measurements at one, three and six months post-treatment
• FDA restricted treatment to fibroids <10cm diameter, less than a total of 100mls volume and only one treatment
Gedroyc discussed his involvement in a study, in which the hypothesis was that 'focused ultrasound will result in a 10-point improvement in Symptom Severity scores at six months post-treatment for 50% or more of symptomatic patients'.
According to Gedroyc, the frequency distribution Symptom Severity score at six months showed that 82% of patients showed significant improvement and in 92% of patients, showed some improvement.
In terms of the UFS-QOL outcome, he reported that benefits appeared early and patients continued to improve, at six months.
GnRh studies
It has been well documented that large fibroids are in most cases difficult to treat because of very large volume and therefore may require a series of treatments. In these incidences, gonadotropin-releasing hormone (GnRh) agonists are commonly administered which introduce a low oestrogen state, (fibroids are oestrogen sensitive). He also stated that the vascularity of fibroids is reduced by GnRh.
In a study involving GnRh agonists, Gedroyc reported that resultant lesions per unit power applied are 50% greater than without pre-treatment. He explained that the belief is that these two therapies, GnRh plus FUS, synergise to allow greater volumes to be treated more rapidly. Early results have shown an increase in total volumes treated per fibroid, said Gedroyc. This therefore has proven a higher rate symptomatic success (Figure 4).
He reported that the Severity Score at six months showed that 74% of patients experienced a significant improvement and 83% showed some improvement after post GnRh and FUS.
Conclusions
Gedroyc concluded by stating that the success of FUS in treating uterine fibroids might be just the beginning, and it points the way forward to the utilisation of this technology in other areas such as the treatment of solid organ malignancies. He also stated that, "Other evolving indications for MRgFUS are palliation of painful bone metastases and treatment of fibroids with a much greater likelihood of maintaining fertility."
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