Dr. Paul Cathcart is a consultant urological surgeon at Guy’s Hospital and St. Thomas’ Hospital in London.
Prostatepedia spoke with him about a clinical trial he’s running that looks at robotic surgery in men whose prostate cancers have come back after focal therapy.
Why did you become a doctor?
Dr. Paul Cathcart: I always liked science; that was my favorite subject. I was thinking about whether to become a vet or a doctor and did lots of school visits. During one of those visits, I met an inspirational character, a surgeon. I spent some time with him, following him around hospital wards and clinics. I thought that he was the sort of person I would like to be: he does the job I’d like to do. I think that’s often the case in life: you meet some inspirational figure who pushes you along one line.
Later on, another inspirational figure who came into my life was a urologist. I was originally going to be a colorectal surgeon. Everything was set for that. Then I met this urologist who showed me the different mix there is in urology, which I found interesting. Then I met Dr. Mark Emberton; I was his research fellow for many years. He’s quite an inspirational person as well. I’ve been working with him for 17 years now on various things.
What is the thinking behind your trial on robotic surgery after focal ablation?
Dr. Cathcart: Focal therapy is a new concept, which Dr. Emberton and one or two other people have pioneered to reduce the side effects and morbidity of prostate cancer treatment. Unfortunately, a proportion of these patients will experience recurrent disease after focal therapy. No cancer treatment is 100% effective. A couple of these focal therapy patients were recurring three or four years after starting the focal therapy program.
No urologist wanted to operate on these patients because they felt that it would be an extremely difficult surgery. In fact, urologists were only offering exenterations to remove the patients’ prostate, bladder, etc.
I got to know quite a few of these patients. (I do a lot of post-radiotherapy surgery, as well.) I decided that this procedure called salvage surgery interested me. We thought that we could do this salvage surgery and maintain good outcomes for our patients because only part of their prostate had been treated during focal therapy. We thought that the side effects of the surgery after focal therapy would actually be a lot less than after radiation, but we needed evidence to prove it. That is why we set up the trial.
We’re also interested in learning why some patients may fail focal therapy. What is it about their disease that leads it to recur? If we can understand why some patients may fail focal therapy, this can help us select up front which patients should have focal therapy and which should not.
What can patients expect to happen during the trial?
Dr. Cathcart: We are halfway through the study at the moment.
Of course, patients undergo a salvage prostatectomy. We take the tissue to be analyzed and look for various genetic markers to see why their cancer may have returned.
This is also a toxicity and side effect study. We have patient-reported outcome measures at baseline and sequentially thereafter. There are a number of blood tests looking at hormone profiles before and after the surgery.
We follow patients for about 12 months after those sequential patient-reported outcome measures; we’re looking to chart that toxicity.
I’ve taken out more prostates after focal therapy than most because of my link with Dr. Emberton. We’re now demonstrating the feasibility and toxicity of salvage focal surgery and trying to understand why these tumors have recurred.
Are you still recruiting patients?
Dr. Cathcart: About 20 patients have undergone the surgery. We’re recruiting 20 more. We haven’t had any adverse events. We were worried about things like rectal injuries, because the rectum can stick to the prostate after focal therapy. We haven’t had any of those.
We’ve actually had a fantastic continence outcome. The prostate cancer community said everyone would be incontinent and impotent, but all our patients so far have been continent.
We’ve got the patient-reported outcome measures to demonstrate it.
The potency rates are taking a little bit longer to return to baseline. The outcomes from potency won’t be as good as the continence outcomes. We haven’t had any side effects at the time of surgery. No complications or anything, so we’re delighted with the way things have gone.
Does the fact that the man has had focal therapy make the potency issues worse?
Dr. Cathcart: It depends on the location of their focal treatment. In those with anterior tumors (tumors away from the neurovascular bundles), we’ve noticed potency returns faster. If they’ve had an ablation on the peripheral zone, near where one of the nerve bundles is located, potency returns more slowly.
We’re also noticing a difference between different treatments. You can give focal therapy with high-intensity focused ultrasound (HIFU), cryotherapy, or something called electroporation. The different energy sources have different effects on the structures surrounding the prostate and a different impact on the chance of potency returning. Electroporation seems to be very precise and leaves the least amount of collateral damage. In those patients, potency returns faster. Cryotherapy creates more periprostatic fibrosis and scarring; potency takes slightly longer for those patients to return. Potency return for HIFU patients falls somewhere in the middle of the modalities.
I’ve also taken out prostates after photodynamic therapy. Photodynamic therapy is better relative to preserving the tissue planes, but it does depend on which part of the prostate has been ablated in the first place.
Is there anything else you think patients should know about your trial?
Dr. Cathcart: We’re going to get a great understanding of why these patients in particular failed focal therapy. The genetic markers and the locations of the tumors will inform which patients are suitable for focal therapy from the beginning. There may be parts of the prostate, or particular types of tumors or genetic markers, which will identify patients best suited to a whole-gland approach such as a radical prostatectomy up front.
It’s not just about the location and grade of the tumor, but also about the tumor’s genetic signature, which may predispose a particular tumor to being better suited for focal therapy.
It’s interesting, in some patients you knock out one tumor say on the right-hand side and that’s it, the tumor never comes back. Other patients’ prostates seem somewhat unstable and have multiple tumors that keep appearing throughout the prostate. I’m sure there is a genetic basis to it.
Because we’re taking out these patients’ prostates, we can analyze all the different tumors. Some people even think that by treating part of the prostate we may be changing the genetics of that tumor—i.e., it gets angrier. I don’t think that’s the case. This study will help prove that point. We’re also going to open up a comparative arm of the study very soon for patients who have had whole-gland radiation or ablation techniques—open to anyone who has had the whole of their prostate treated with brachytherapy, radiotherapy, HIFU, or cryotherapy. We’ve been finding that patients who have had surgery following focal therapy have better outcomes than those who have had whole-gland therapy up front. We’re going to recruit into that second arm to demonstrate that surgery after focal therapy has a better outcome.
Can non-UK residents come to you for surgery?
I’ve got a clinic called the Recurrent Prostate Cancer Clinic. I have a reasonable number of patients who come from the United States. They normally come to Dr. Emberton for focal therapy, then if they develop recurrent disease, I operate on them. A lot of urologists wouldn’t operate on these patients. Certainly, in the United States, hardly anyone operates on post HIFU patients simply because HIFU has not been available until very recently.
How does newer imaging like gallium-68 PSMA PET/CT impact salvage focal therapy?
Dr. Karnes: PET imaging has been good at detecting metastases, but in terms of imaging the primary tumor, the resolution hasn’t been the best. Now, we and others are moving into a PET/MRI scan.
That is a fusion scan?
Dr. Karnes: A fusion scan with MRI rather than the PET/CT. Obviously, an MRI provides more resolution of the prostate. To me, MRI is obviously the gold standard when it comes to imaging the primary prostate. We’re certainly using the technology. Others are using it. We don’t really know what the exact accuracy is of the MRI/PET fusion scan in those who have had radiation failure.
And, as I mentioned, I don’t think we have really much in the way of a clue regarding the biology of this index lesion in radiation-recurrent cancer in the prostate. I think that in the glands of men who recur after radiation, there is probably higher tumor burden compared to the newly diagnosed patient.
A third problem we have when it comes to focal salvage therapy is that I don’t think we even have a great definition of what constitutes a potential local recurrence after primary radiation. The Phoenix definition used by the American Society for Radiation Oncology is the nadir (or lowest) PSA plus 2. This definition predicts recurrence, but what it really predicts is progression, not necessarily local recurrent disease.
In this country, for many men who fail radiation, the next treatment is hormonal therapy. Hormonal therapy really has only a palliative intent and won’t cure anyone of localized radiation-recurrent disease.
We need to do a better job of appropriately diagnosing radiation failure patients in the first place. What that better job would be, I don’t know. I don’t think routine biopsies, which have been looked at in the past, are the answer. But perhaps imaging sooner rather than waiting for the Phoenix definition makes sense. Maybe, as you mentioned appropriately, with the newer PET/MRI fusion scans, we can image men sooner to try to detect a local recurrent disease earlier.
That being said, I do a lot of salvage radical prostatectomies, almost one a week. This is unpublished, but I have not seen a big stage migration (less extraprostatic extension and/or nodal metastasis) in the last decade. I still see a lot of patients with radiation failure; they come to their salvage prostatectomy with seminal vesicle invasion and nodal disease. Up to a third of patients will have seminal vesicle invasion and I see nodal involvement in up to 20% at salvage surgery.
Why is that relevant to salvage focal therapy?
Dr. Karnes: A lot of the seminal vesicle invasion is not always evident on MRI. And a lot of these patients don’t get routine biopsies of their seminal vesicles. If they undergo a salvage focal therapy, their doctors are obviously going to be missing a significant component of their disease because salvage focal therapy, in my opinion, doesn’t work to ablate the seminal vesicles. Obviously, salvage focal therapy can do a job in the gland itself, but in the appendages, such as seminal vesicles, it is hard to get an appropriate ablation of the entire seminal vesicles because of the risk to adjacent structures— the bladder, the ureters, and so forth.
Another thought I have about salvage focal therapy is when we look at other forms of ablation technologies like cryotherapy or HIFU, we’ve morphed them from whole-gland to focal and now to focal salvage therapies. But I don’t think we even know who the ideal candidate is for whole-gland HIFU or whole-gland cryotherapy let alone the focal form of the therapies in a treatment-naïve patient. Obviously, these are alternatives or options for patients who are newly diagnosed, but more troubling for me is this: I don’t think we know exactly what constitutes a success. How do we monitor whole-gland cryotherapy or whole-gland HIFU? We’ve used PSA failure as a definition, but are we really using the right tool to monitor?