Although high-intensity focused ultrasound (HIFU) has not yet been approved in the United States for the treatment of prostate cancer, a growing number of the nation’s urologists are offering this noninvasive surgical procedure at centers located outside the country.
Renal & Urology News asked urologic oncologist David Y.T. Chen, MD, FACS, of Fox Chase Cancer Center in Philadelphia, about his impressions of HIFU as an investigator in a trial featuring the treatment.
How does HIFU work?
Dr. Chen: The general concept is similar to the idea of sunlight on a sunny day: If you hold a magnifying glass, you can focus that sunlight to a point that it generates heat and can cause a fire.
From a physics standpoint, the HIFU concept is the same in that you can take a lens and focused waves, concentrating them on a single location called the focal point, and just as much as you can start a fire with sunlight, you can generate a lot of energy at this focal point using sound waves.
The instrument itself is not specifically special or unique or even medical in its idea; it’s physics. It’s applying the physics of sound waves and how you can focus that energy to a location to create heat—it’s the heat that potentially has a role and can be of medical value.
Why is HIFU being tested for the treatment of prostate cancer?
Dr. Chen: The theoretical appeal is that HIFU is noninvasive because it passes sound waves through a broader area of tissue and then, at a point away from where the energy is projected, it coalesces to generate heat.
Most of the attention on this technology is probably related to its application for prostate cancer, but that’s not the only application for this. For example, this approach, using a different type of machine than is used for prostate cancer treatment, is approved in the United States to treat benign uterine fibroids. The two machine systems for prostate cancer use are approved by the European version of the FDA.
I got involved [with HIFU research] partly to get some personal experience on machinery that may or may not be of utility, and to determine the appropriate way to test this.
What is your involvement with HIFU?
Dr. Chen: I have no commercial ties to this, and I do not perform the procedure outside of the confines of the trial at my institution. The company that manufactures the Sonablate 500 machinery [one of two HIFU systems approved in Europe for the treatment of prostate cancer] is in the process of a trial that is registered with the FDA, and I’m one of the investigators.
This study has been open nationally at about 15 centers, and has been open at our hospital for a little more than a year. I believe that we’ve treated seven patients so far, roughly one patient every other month. The trial is specifically for men who have been “caught in the window”—that is, men who have had prior external radiation therapy that did not eliminate their cancer, but whose cancer has not yet metastasized.
Several U.S. urologists are willing to go out of the country to perform HIFU. Isn’t that an unusual amount of support for a treatment that’s not approved here yet?
Dr. Chen: Patients in this country, not surprisingly and perhaps appropriately, are looking for a perfect treatment for whatever their problem is, prostate cancer included, and prostate cancer is particularly sensitive due to the very personal effects that often result from treatment.
So established, effective treatments exist, alternatives are being pursued in hopes that they may have less of an impact on urinary function or sexual function than standard treatment. But I think ultimately, HIFU will not have any less of an impact than anything else, simply because the prostate is surrounded by very important structures and it’s very likely that these structures get some level of exposure to this HIFU-created heat.
Any patient from the United States who wants to have this procedure has to pay for it out of pocket since it is not FDA-approved and therefore not recognized by U.S. health care insurance or reimbursement payers of any type.
The difficulty in my feeling comfortable endorsing this treatment is I’m personally not convinced it’s any better than anything that is currently available, and if it’s not any better, there’s not a great motivation on my part to suggest someone should have it done other than if I was going to get paid directly for it. I can’t think everybody does that for that financial motivation, but I would say it is an unavoidable potential conflict of interest.
But with respect to noninvasiveness, doesn’t HIFU offer something that the other treatments don’t?
Dr. Chen: Radiation is also noninvasive. The idea that it’s not invasive does not mean that it is without risk and without side effects. You could stick your entire hand in an ice bath until it was frozen solid and that’s not invasive, but your hand would be seriously injured. Similarly, you could have very severe complications from HIFU therapy even though it’s noninvasive, because essentially you’re destroying tissue, burning tissue, by the amount of heat that this energy creates at certain places.
Are those complications worse than those associated with existing therapies?
Dr. Chen: My personal opinion is, HIFU is not without a risk of complications that is any different than the risk of complications for other treatments for prostate cancer. I haven’t treated enough patients to say that the degree of risk is better or worse.
I do think it is important to emphasize that a treatment like this does not avoid the potential of any of the recognized side effects of prostate cancer treatment, such as incontinence or impotence.
Aside from whether the treatment itself is easier or less dangerous, patients in general can have other medical issues—heart disease or lung issues, for example—where just the process of putting them under general anesthesia is dangerous. They can’t avoid general anesthesia with HIFU, but they can be treated for prostate cancer with radiation therapy, which can be done without any anesthesia whatsoever.