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Conversations With Prostate Cancer Experts


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Dr. Daniel George on PSA Recurrence

Dr. Daniel James George is Professor of Medicine and Professor in Surgery at Duke University.

Prostatepedia spoke with him recently about biochemically recurrent prostate cancer.

Have you had any patients whose cases have changed either how you view your own role as a doctor or how you view the art of medicine?

Dr. Daniel George: As we evolve new therapies and indications for treatment, it’s really interesting how that affects our relationships with patients. As an oncologist, my relationships with patients have become more longitudinal. What I mean by that is: people are living longer than ever. I’m beginning to recognize my treatments in the context of not just the short-term endpoint of how to control my patient’s disease in the next few months but in terms of the ramifications for his life and long-term survival. What does it mean in terms of his functional well-being, not simply now, but in a year from now or five to ten years from now?

In many ways, it comforts patients to hear the perspective, that I see them as a long-term survivor, and that I’m thinking about the implications of our treatments in a long-term perspective. That helps the patient invest in his own life and well-being for the long-term, whether that be diet, exercise, sleep, or all these other behavioral interventions that can really impact their quality of life.

You’re basically saying that prostate cancer is becoming more of a chronic disease.

Dr. George: It has been for some patients, and we’re beginning to recognize it more and more for all patients.

We used to think of short-term goals for some of our most advanced cases of prostate cancer—just in terms of disease control or palliation and not worry about the long-term implications of treatment. While on the other end of the spectrum we would have cases where we don’t have to treat the disease at all or maybe treat it minimally in others. Now I’m recognizing prostate cancer as a chronic disease for everybody, and so everybody needs to think of the long-term implications of treatments.

Likewise, we need to think of the implications of our sequential therapies and their cumulative side effects.

Can you define M0 prostate cancer, or biochemically recurrent prostate cancer, for patients?

Dr. George: This is probably confusing because of its name. We refer to prostate cancer in terms of stage. Stage refers to the extent of the disease. The Gleason Score or grade refers to how it looks under the microscope, its aggressiveness. But stage refers to the progression of this disease. Do they have bone metastases? Do they have distant lymph node metastases or other sites of disease? Or is it localized?

We usually use three categories: the T stage, which is the localized tumor, the N stage, which is the lymph node status, and then the M stage, which is the presence of metastases that are distant from the prostate. M0 refers to patients who have no distant metastasis. Think of M0 in terms of patients who are newly diagnosed with prostate cancer.

Recurrent prostate cancer patients are those who’ve had local therapy, surgery, or radiation, and who now have evidence of disease recurrence by PSA. After these treatments, we know that your PSA should be 0 or very low, and it should stay low. If your PSA rises and continues to rise, that’s an indication of disease recurrence. Yet, in many cases, they’re what we call M0 because, when we stage the patient with a bone scan or a CT scan, we can’t see any evidence of cancer. Many of those patients have what we might otherwise refer to as microscopic metastatic disease, disease that’s just below the level of detection. Some of them could have local recurrence or recurrence just within the pelvis and regional nodes that’s not distant. We now know from recent studies that the majority of those patients are going to relapse with distant metastatic disease. In other words, they have distant metastatic disease, but it’s just below the level of detection.

So, this is a bit of a misnomer because we’re treating them with systemic whole-body treatment therapy now because we recognize the risk of distant metastatic disease for the majority of these patients. We’re beginning to use newer imagining techniques, such as PET scans, that could be more sensitive at picking up this microscopic metastatic disease. That shouldn’t deter us from applying the current data to that patient population.

I think of M0 prostate cancer as being low-volume castrate resistant prostate cancer. When we think of it that way, it makes sense that the drugs we’re using work and work even better in that low-volume population. We should use them because M0 is just an early continuation of that metastatic process.

What are these systemic approaches that patients are likely to receive? What are the implications down the line in terms of side effects, and in terms of the longer longitudinal quality of life issues you mentioned earlier?

Dr. George: This is an important aspect of the care for these patients because we have two studies—and a third will soon be reported—that demonstrate a clinical benefit from using what we have broadly termed secondary hormonal therapies, therapies that we add to primary androgen deprivation (ADT) or testosterone suppression.

Patients for whom testosterone suppression has failed can respond to another hormonal intervention later. These are drugs that target the androgen receptor, the protein that testosterone binds to, and inhibits it from signaling. It shuts off what seems to be the most common mechanism for resistance to testicular testosterone suppression. That is an overexpression or overabundance of this receptor, which makes prostate cancer cells sensitive to low levels of residual testosterone in the body.

Xtandi (enzalutamide) and Erleada (apalutamide), in two separate Phase III studies, have demonstrated a clinically significant benefit: a delay in the time to metastasis. The FDA has accepted this as a meaningful endpoint because of the degree of delay. It was associated with about a two-year delay in the time to metastasis in this population.

Patients who were at high risk for developing metastatic disease were in the control arm and developing metastatic disease within about a year of coming on the study for the placebo arm. For the treatment arms, with Xtandi (enzalutamide) or Erleada (apalutamide), we’re seeing a delay of about two additional years. That means three years until the time of metastasis.

The results suggest that we’ve changed the progression of this disease dramatically. In addition, both studies showed a strong trend in favor of the treatment arm for improved overall survival associated with this delay in metastasis. Even though the data may not be as complete because it takes a longer time to report, we’re seeing this correlation in metastasis-free survival, if you will.

Again, I caution the semantics here because these patients do have metastases; they just can’t be seen yet. But the delay in that radiographic appearance of metastasis is associated with an improved survival.

What’s the approach to finding smaller metastases earlier on with the newer imaging techniques? And if they are very small, do you treat them aggressively with radiation, do you continue using the systemic therapies, or do you use a combination?

Dr. George: There is a mix of presentations of patients. When we image with a novel PET-imaging tracer, we’re going to see more than one site of disease in most patients. We’re going to see multiple lymph nodes, multiple bone metastases, or maybe lymph and bone metastases.

For a subset of about 20 percent of patients, we see this disease limited to only lymph node disease or only one or two bone metastases. We refer to this as oligometastatic disease, which we have yet to biologically define. Clinically, we know that it’s associated with a longer survival.

Oligometastatic prostate cancer raises the question of whether or not these patients could be managed with therapy localized to those sites, therapy that does not necessarily expose them to further systemic therapy. We don’t have a lot of data in the castrate-resistant setting, but in the hormone-naïve setting, there are some data that suggest that there can be a delay in the time to initiating subsequent hormonal therapy by doing that.

There’s a study out of Europe, but the median effect was relatively small, just a few months. It’s not clear that this is going to be a meaningful difference for most patients, but it is something that can be discussed.

A lot of those treatment approaches can be done with minimal intervention, external radiation, ablations, or limited surgery. Those will be options. But in the majority of these patients that we do this molecular imaging for, we’re going to find evidence of more than one site of disease or multiple lesions. This suggests that they need a systemic therapy approach.

It’s reasonable to extrapolate this data because we know from the placebo arm of these studies that these patients went on to develop metastases in their bone scan or CT scan within months, 50 percent of them within a year, and many of them in just a few months of their subsequent scan. The likelihood is, if we’d done the molecular imaging at baseline on these patients,we would have seen it. Yet still, in this population, we’re seeing a treatment effect.

We see the treatment effect regardless of what level of PSA doubling time you have. In patients who have a PSA doubling time of just two or three months, we see a dramatic treatment effect. In patients who have a doubling effect of eight or ten months, we still see a dramatic treatment effect in terms of prolongation in the time to metastasis—fewer events in those cases, but still, we see that treatment effect.

The PSA doubling time is an important parameter that we’re using now, in addition to these imaging stats, to determine who we should treat with these drugs and their prognosis.

Isn’t doubling time an indication of the aggressiveness of the disease?

Dr. George: It is. We knew this earlier in disease prior to hormones. PSA doubling time was very prognostic for time to metastasis and overall survival. It’s been less studied in the castrate-resistant setting, when patients have progressed on primary hormonal therapy, but we’re still seeing it there. In fact, the results are really dramatic.

There were some abstracts at the Genitourinary Cancer Symposium (GU ASCO) around this data. There have been reports from these two Phase III studies with Xtandi (enzalutamide) and Erleada (apalutamide) that demonstrate this. We believe there is a strong correlation between a shorter PSA doubling time—a shorter time to bone metastasis—and shorter overall survival.

Just to put these studies into context, the requirements were that PSA doubling times were less than ten months. If doubling time is a year or longer, these are slow-growing cancers. Even though they’re castrate-resistant, these are patients who will live for many years with no metastasis, so it’s reasonable just to observe their disease. For the studies, the median or 50th percentile PSA doubling time was around four months. That’s really short and aggressive.

That’s why we saw that the average time to metastasis was just about a year in the control arms. It’s important to recognize where your patient is in this continuum because it guides whether we should treat him like we did on the study, or if their disease is too slow growing to justify the treatment.

What other considerations are important for patients who fall into this category?

Dr. George: The important thing for patients to know: not to worry. I know that as a physician, it’s easy to say ‘don’t worry about your rising PSA level,’ but as a patient, it is hard to ignore.

Join us to read the rest of Dr. George’s comments about biochemically recurrent prostate cancer.


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Join A Clinical Trial For Biochemically Recurrent Prostate Cancer

Dr. Rahul Aggarwal is an Associate Clinical Professor of Medicine in the University of California, San Francisco Genitourinary Oncology and Developmental Therapeutics programs. He’s keenly interested in developing novel therapeutics and imaging strategies for men with advanced prostate cancer.

Dr. Aggarwal is a Co-Investigator in the ongoing Prostate Cancer Foundation’s Stand Up To Cancer-funded West Coast Dream Team prostate cancer consortium.

Prostatepedia spoke with him about his clinical trial on hormonal annihilation in men with high-risk biochemically recurrent prostate cancer.

Not a member? Join us.

What is the thinking behind your clinical trial on hormonal annihilation in men with high-risk biochemically recurrent prostate cancer?

Dr. Aggarwal: This trial is for patients with prostate cancer who previously had what we call a radical prostatectomy, or the prostate was removed, as their primary treatment and then subsequently had evidence of cancer recurrence as indicated by a rising PSA. We’re specifically looking at patients with a PSA that is rising quickly with a PSA doubling time of nine months or less.

We know that this group of patients is at risk for subsequent development of metastases as well as at risk for prostate cancer-related mortality. One standard treatment approach is to use intermittent hormone therapy, which can suppress the cancer for a period of time. Inevitably, though, the cancer becomes hormone or castration-resistant.

Once that happens, patients have fewer treatment options remaining and a shorter prognosis.

The main goal of the study is to use some of the more potent hormonal therapies that have been developed, including Zytiga (abiraterone) and Erleada (apalutamide). and apply them to this situation to see if we can durably suppress the patients’ prostate cancer in a finite period of treatment. Rather than treating indefinitely, we treat everyone on the study for 12 months, and then we stop and let their testosterone levels recover and any side effects related to hormone therapy stop or lessen. Hopefully, we can see long-term control of patients’ PSA levels or maybe for some prevent the need for future treatment.

In this way you would also lessen some of the side effects associated with these treatments?

Dr. Aggarwal: Exactly. Then the total duration, or percent time, spent on hormone therapy would be shorter. Even though we’re giving more potent hormone therapy, this would actually translate into less overall treatment and less medical burden from a side effect perspective. Some of the other studies that have come out using medicines like Zytiga (abiraterone) and Erleada (apalutamide) in the hormone sensitive or castration resistant settings do seem to suggest there is a benefit to giving these medicines earlier in the treatment course. I think it fits with what we’re seeing in terms of the general trends in the use of these medicines and the management of prostate cancer.

What can a patient expect to happen step by step if he ends up participating?

Dr. Aggarwal: The treatment phase of the study consists of monthly visits for a year in which patients are getting hormone injections. Then it is a randomized study, so in the standard of care arm men would be getting the hormone injections alone once a month for a year. Then there are two experimental, or investigational, arms with added hormonal therapy. One arm has added Erleada (apalutamide). The third arm adds Erleada (apalutimide) plus Zytiga (abiraterone).

Patients have a two in three chance of being on one of the added hormonal treatment arms.

This is an open label trial, meaning there is no placebo. Everyone will get active treatment, so there’s no risk that their PSA levels won’t go down. Every patient responds initially to hormone therapy, or nearly everyone. We see patients monthly for hormone treatments. We evaluate them for side effects. At four or five time points throughout the study, we have patients fill out questionnaires regarding their symptoms. We do want to understand from a patient perspective what quality of life and symptoms are like during the course of treatment.

After one year of treatment, assuming the PSA is not rising, patients will then enter a follow-up phase which we try to make easy. We check patients’ PSA and testosterone levels once a month, but we don’t require any mandated in-person visits to allow more flexibility for those who live far away from the study center where they were treated.

At the time that the PSA rises to above 0.2, that’s the cut off for what we call PSA progression, which is the primary endpoint of the study. After that treatment is per the discretion of the patient and treating doctor. We still follow patients long term for metastases free and overall survival. The treatment options at that point are completely up to whatever is decided upon between the patient and his doctor. It’s flexible on the backend too if his PSA were to rise.

Join us to learn more about Dr. Aggarwal’s trial and how to participate.