“Soundwaves could help 95% of prostate cancer patients … without affecting sex life,” the Daily Mirror reported today. Its story comes from a small study that looked at an experimental treatment using high-intensity focused ultrasound (HIFU) to target areas of prostate cancer in men where the disease had not spread.
Standard treatments for prostate cancer often lead to undesirable side effects, in particular erectile dysfunction and urinary incontinence. Researchers found that a year after this experimental treatment, 89% of men still had erectile function and all were still continent. Ninety-five per cent of the men showed no evidence of disease on an MRI scan.
The results of this small study look promising. Men with early (localised) prostate cancer that has not spread can often live for years without developing life-threatening symptoms, and are often faced with a difficult decision about whether or not to have conventional treatment, which can have side effects. A treatment that can target areas of cancer without damaging healthy tissue might enable more men to have treatment for prostate cancer at an early stage.
However, it’s important to point out that this is an early “proof of concept” study and that a far larger trial is required to assess both its effectiveness and safety.
Where did the story come from?
The study was carried out by researchers from University College London, and was funded by the UK Medical Research Council, the Pelican Cancer Foundation and St Peter’s Trust. The study was published in the peer-reviewed medical journal The Lancet Oncology.
The media reports were generally fair. The Daily Mail’s headline that the new treatment “zaps” prostate tumours was perhaps misleading. The study was intended primarily to assess the frequency of side effects of treatment, rather than its success in treating prostate cancer. Most papers neglected to say that this was a trial of a treatment for early (localised) prostate cancer, which has not spread to other organs or tissue. Its findings do not apply to more advanced disease.
What kind of research was this?
This was an early (prospective development) study looking at a new treatment for localised prostate cancer called high-intensity focused ultrasound (HIFU).
Prostate cancer is the most common cancer in men, yet, as the authors point out, treating localised prostate cancer is difficult since the disease often progresses slowly and may not cause any symptoms for many years. There are several standard treatments for localised prostate cancer. Some involve treating the whole prostate with radiotherapy or removing it with surgery, and these can damage surrounding healthy tissue. The more destructive treatments of the whole prostate gland lead to undesirable side effects, in particular, erection problems (affecting 30-70% of men treated) and urinary incontinence (affecting 5-20%). One alternative for men at present is to have no active treatment but to undergo regular checks. This is known as active surveillance.
The new treatment, say the authors, is less aggressive and able to target the cancer site rather than the whole organ. In this respect, it is similar to treatment for other malignancies, such as localised breast cancer (where a lumpectomy is now an alternative to mastectomy). They say that in a previous study they had used HIFU to destroy one half of the prostate where the cancer was situated. But they point out that only one in five men have disease in one half of the prostate only. Their new study looked at whether HIFU could be used for treating cancer at specific sites within the prostate.
What did the research involve?
Between 2007 and 2010, the researchers recruited 42 men to their study. To be eligible they had to be aged 45 to 80 years and have been diagnosed with localised prostate cancer ranging from low to high risk. They also had to have had no previous treatment for prostate cancer or other conditions of the prostate and they had to be fit for a general anaesthetic and for MRI scanning. At the start of the study, they were also asked about whether they suffered from erectile dysfunction or urinary incontinence.
In order for researchers to pinpoint the exact location of their cancers, all the men underwent two diagnostic techniques – a special type of MRI (magnetic resonance imaging) scan and a “mapping” or “template guided” biopsy.
The patients, under general anaesthetic, then underwent the treatment with an HIFU device, a probe inserted close to the prostate through the rectum. The device emits high-frequency sound waves that heat the targeted cells to 80°C. Researchers ensured that general guidelines for all treatments were followed, in order to protect nerve cells and healthy tissue.
The men were followed up at one, three, six, nine and twelve months. On each occasion they were given a PSA blood test (which measures levels of prostate specific antigen, a chemical marker that can indicate the presence or recurrence of prostate cancer), and were given validated questionnaires asking about side effects. At six months they had a further MRI and a biopsy. Men who had a positive diagnosis were given further HIFU treatment. A further MRI scan was carried out after a year.
The researchers were primarily interested in whether the treatment was acceptable and in rates of side effects, in particular erectile dysfunction and urinary incontinence. Quality of life was assessed, and the reasearchers also looked at the progress of the cancer.
What were the basic results?
The researchers included 41 men in their final analyses as one man died of unrelated causes three months after focal therapy. Of these, 30 (73%) had intermediate and high-risk disease.
The main findings following treatment with HIFU were:
- At six months, 30 of 39 men who had a biopsy (77%, 95% confidence interval 61 to 89) showed no evidence of cancer and 36 men (92%, 95% confidence interval 79 to 98) were free of clinically significant cancer.
- At 12 months, after treatment was repeated in four men, 39 of 41 (95%, 95% confidence interval 83 to 99) had no evidence of disease on an MRI scan.
- At 12 months, of 35 men who had no erection problems at the start of the study, 31 (89%, 95% confidence interval 73 to 97) had erections sufficient for penetration.
- Of 38 men who had no urinary incontinence at the start of the study, all were leak-free and pad-free at nine months. Of 40 men who did not use pads at the start, all were pad-free by three months and maintained pad-free continence at 12 months.
Some men suffered mild side effects after the treatment, such as urinary tract infection. Two men were admitted to hospital for acute urinary problems.
In these 41 men with an average PSA blood test of 6.6ng/ml, there was a significant decrease in PSA levels at 12 months.
How did the researchers interpret the results?
“Focal therapy of individual prostate cancer lesions leads to a low rate of genitourinary side effects and an encouraging rate of early absence of clinically significant prostate cancer,” the researchers say.
The results of this small early trial are promising, but a large-scale randomised controlled trial comparing the effectiveness and safety of the new treatment with both standard treatments and “active surveillance” is now needed. As the authors note, the study had several limitations:
- It was a small observational study of 41 men.
- It was an uncontrolled trial. This means that there was no group who did not receive treatment (control group) against which this treatment could be compared. This is because it was designed primarily to assess the rate of side effects associated with the new treatment and not its effectiveness in combating prostate cancer.
- The authors refer to other ablative therapies as well as brachytherapy and image-guided radiosurgery, which can be used to treat smaller volumes of prostate tissue while seeking to preserve function. These have not yet been assessed against this ultrasound focal therapy.
As an early “proof of concept” study the results will probably be used to support and design larger trials to assess both effectiveness and safety of HIFU compared to current best practice.