Imaging Prostate Cancer
Posted: Nov 01, 2018
POSTED: April 15, 2019
Dr. Ahmed is Professor and Chair of Urology at London’s Imperial College Healthcare.
His research focuses on prostate diagnosis using novel imaging and tissue biomarkers, prostate treatments that reduce the harms of traditional surgery and radiotherapy, and clinical trials and health technology evaluation.
Prostatepedia spoke with him about the current state of focal therapy for prostate cancer.
Dr. Ahmed: Focal therapy is about targeting the tumor within the prostate with a margin of normal tissue. The tumor is one that we believe that were we to leave it untreated, would progress, grow and spread, and impact the patient’s life at some point. By doing so, we avoid treating the entire prostate. We avoid damaging as much normal little tissue as possible. By damaging as little tissue as possible, we aim to maintain as much function as possible for that particular man, whilst at the same time treating the cancer that would otherwise cause problems in the future.
Dr. Ahmed: It is an umbrella term. I often joke that there’s almost like a catwalk of treatments that can be used for focal therapy. The traditional ones were cryotherapy, which freezes the tissue, and high intensity focused ultrasound (HIFU), which uses very focused ultrasound waves that heat up the prostate. You can use laser, which also heats up the prostate. You can use electrocution of the cells, which is called irreversible electroporation. There are now some new injectable drugs. You can inject hormone drugs or molecules that are activated by PSA, which then kill the prostate cells once they are injected into the prostate. There’s a lot of activity going on.
What I often say is that all of these different modalities are interesting. It’s good to see that commercial bodies are really interested in this field. That shows that the concept has real legs and everybody sees this as a big future, so that everybody’s crowding into the market. Ultimately, these are all tools, if you like— surgical instruments for me to do my focal therapy. No one tool can be applied to all tumors.
Let me take an example. If you had a big prostate with a tumor high up in the gland, there’s no way HIFU would be able to reach it. The ultrasound wave just can’t get that far. Even if it could, by the time it reached the tumor, there would be so much tissue it went through that it would lose its energy. For that particular tumor, an anterior tumor, something like cryotherapy is probably going to be better for that particular man than HIFU. A posterior tumor near the rectum, but contained in the prostate, probably does really well from HIFU at the moment, but could easily be treated in the future using these injectable drugs, if they’re to be efficacious.
Which form of focal therapy is best really does depend on where the tumor is, how big it is, and how big the man’s prostate is. Are there other characteristics within the prostate, for instance, like calcification, which means you can’t see the tumor? Those calcifications might, potentially, deflect the energy. There are a lot of other considerations, but there are quite a lot of things that you can use. I would say the two that are in pole position at the moment, just because they’ve been around for longer and therefore they have a lot of data, and the two that I use routinely in clinical practice, are HIFU and cryotherapy.
Dr. Ahmed: Firstly, focal therapy is a choice for the man who wishes to preserve or minimize his risk of genitourinary side effects like incontinence and erectile dysfunction as much as possible. You could argue that everybody wants that, but there are some men who will just have radical treatment and say to me, “I understand that I have side effects, but I just want it sorted out.” There are other men who prioritize minimizing the genitourinary impact that treatments have.
Focal therapy is also a good choice for men who have one index lesion. In other words, they have one tumor that is clinically significant, but at the same time have either no other tumors or one or two clinically insignificant cancers. In those men, we would target the main, biggest, or highest grade tumor because that is the one, studies have shown, that is likely to grow, progress, and metastasize if it was left on its own. The other, smaller, low-risk lesions are the type of indolent disease that a lot of men in the male population have that doesn’t need immediate treatment. You can monitor those after you’ve knocked out the main tumor, for instance.
Dr. Ahmed: One of the reasons is it’s difficult to localize one or two millimeters of low-risk disease. In order to treat those, you’d have to end up treating a block of tissue. By the time you’d treated that block of tissue, or two other blocks of tissue, you’re probably at 70 to 80% of the prostate volume.
Dr. Ahmed: You might as well just treat the whole thing because you’re going to cause as much damage. These small lesions are often not visible on MRI. They’re found on random, systematic biopsies, and you have no idea exactly where they are.
Another consideration is the characteristics of the lesion itself that we would want to treat. It could be one of two things: intermediate Gleason Grade 7, so 3+4 or 4+3. Or, there’s an increasing recognition that high volume Gleason Grade 6 is also something that is better treated immediately than monitored because that is also likely to progress.
For unfavorable, if you like, low-risk disease and intermediate-risk disease where there is one index lesion you can carry out focal therapy. If you can have intermediate-risk disease, which has two or three significant lesions, you would be better served having radical therapy.
Dr. Ahmed: This is quite an important topic now. We know that following focal cryotherapy, focal HIFU, and some of the newer emerging focal therapy modalities that about 15 to 20% of men will either have residual or recurrent disease in the area that’s already been treated. Most of those men will be eligible to have a repeat session of HIFU or cryotherapy. Certainly in my practice, I tell men there is a one in five chance that we may have to repeat the focal therapy to the same area. Almost invariably, all men see that as just part of the intervention. I would argue having two treatments in a fifth of men is probably part of the treatment.
If they fail two treatments in that area, then they really should go on to have radical therapy, or a change in the type of treatment that you give. If the cancer has resisted 80 to 90 degrees centigrade temperature changes twice, or with cryotherapy minus 50/minus 60 degree centigrade twice, then that is an aggressive tumor. It probably has got a very aggressive blood supply and we need to change tacks.
There is a group of men who develop new lesions in untreated tissue. Some of those men can have another focal therapy, but most of them will go on to have radical therapy because their untreated tissue, if you like, has declared itself as unstable. It has a propensity to develop new tumors, and therefore, it would be better to treat the entire prostate.
About 15 to 20% of men over five to six years need a second focal therapy treatment. Overall, about 5 to 7% of men go on to have radical therapy, despite one or two focal therapy sessions. Now that is five to six-year data; we don’t have ten-year data at the moment, either from HIFU or cryotherapy. The newer modalities don’t even have five to six-year data.
Dr. Ahmed: I guess it depends on how you define that level of evidence. If we have to wait ten to fifteen years, then yes. If you argue that we’ve now got good five to ten-year data showing non-inferior cancer control, superior toxicity, or superior side effect profiles after focal therapy, then there are a considerable group of men who will accept the uncertainty of the lack of ten to fifteen-year data. They prioritize genitourinary function and they are not compromising their cancer control, at least at five to six-years median follow-up. And they can still have surgery or radiotherapy afterwards.
In the United Kingdom, in certain centers, focal therapy has been offered side by side with other radical therapies within the National Health Service, as part of the NICE, or National Institute for Clinical and Healthcare Excellence, approvals that we have.
Dr. Ahmed: There are a number of controversies. One big controversy is this lack of ten to fifteen-year data. I was in the European Congress a couple of days ago. There was a Pro/Con focal therapy argument. I was pro and the person before me was con. He stood up and said, “We don’t have fifteen to twenty year data.” Five years ago, we didn’t have five-year data. A couple of years ago, it was you don’t have ten-year data. When we first started, they said well you don’t have any one year data on biopsies. This is the first time I’ve heard people stand up and say, well you don’t have fifteen to twenty-year data. It’s slightly amusing. It’s infuriating, as well, because the goalposts keep on changing. The long-term data will come; we’re collecting all the data in registries in the United States, the United Kingdom, and European centers. It’s all very robust data collection. We’re doing trials to see if men will accept randomization between radical and focal therapies. Those trials are tough. Men generally want to choose their therapy rather than allowing themselves to be randomized, but we’ll see.
Then the other controversies are around the areas that we touched on. What happens to the untreated tissue? So far, about 4 to 5% of men over the five to six years of median follow-up that we have in our series of several hundred cases have developed new lesions in untreated tissue. Now, those are probably just tiny bits of Gleason 7 tumors that the biopsy and MRI missed that then subsequently progressed. Some of them will be new lesions, but some of them will be disease that was missed in the first place, which declare themselves later. By ten years, it might be higher. So far it’s quite low.
One of the arguments against focal therapy is that this is a multi-focal disease. The untreated tissue is just going to show up with lots and lots of cancers, but that has not been the case, so that has been quite reassuring. The other controversy is around the point that MRI is not good enough and biopsy is not good enough. But I think both MRI and targeted biopsy are good enough. You can never be 100% in anything. If you look at breast mammography, the data shows that a negative mammogram can miss anywhere between 5 to 30% of breast cancers, yet we still use it as a screening tool. We all accept that nothing in medicine is certain. Then there’s concern about what happens to men who fail focal therapy. Can we remove the prostate, or are these men too scarred. What happens in terms of their cancer control? It’s early days yet, but certainly technically, removing a prostate after focal therapy is easier than removing a prostate after failed radiotherapy. It certainly is more scarred around the treated area, though. Does that mean men shouldn’t have focal therapy?
I would argue not because we’re giving radiotherapy to hundreds of thousands of men. It’s an accepted treatment modality, and if it does fail, it’s tough surgery afterwards. That is, unfortunately, the nature of the beast. When the first treatment fails, secondary treatments are always going to be a little bit more difficult, if not a lot more difficult.
Dr. Ahmed: The concern is both. If it’s more difficult to perform, then are they likely to suffer more side effects? And, as a result of the surgery being difficult, are we going to get more positive margins? Are they going to fail more often?
These are men whose tumors are going to be very aggressive by nature because, as I said, they resisted extremes of temperature, sometimes twice, and there are still a few cells. So they’re going to be pretty aggressive. The failure rates might be higher in that group, just because of the focal therapy paradigm. Just like radiotherapy, when you get radio-resistant cancers they are generally more aggressive and nastier cancers just by natural selection, if you like.
Dr. Ahmed: It’s very important when you are first diagnosed with prostate cancer not to rush into treatment. It’s important to do as much reading as you can and have consultations with urologists and radiation oncologists. If you haven’t been told about focal therapy, ask whether you’re suitable. You might get an answer that says, “Well, it’s not proven.” But if you are keen to explore it, you should definitely have a consultation with somebody who does focal therapy so that they can tell you first whether you are suitable, and secondly, what the outcomes might be in your case. I think every good focal therapist will share the uncertainties, as well as the certainties, around the treatment that they give.
If they’re not sharing those uncertainties, then see somebody else. It’s also very important that they quote their own data. That data, ideally, should be published in the public domain because that is a sign, first of all, that you’re being told the right outcomes for that surgeon or physician. Also, it’s a sign that physician takes their trade seriously and is constantly looking to see how they can improve, as well as sharing their data with their peers.