Category Archives: Prostate cancer therapy

February 20, 2022 · 6:18 pm

Prostate cures…at any cost?


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This week brought excellent and exciting news from the ASCO GU Meeting about management of high risk prostate cancer using “triple therapy” for metastatic disease. Adding further evidence for the “kitchen sink” approach, Matt Smith from MGH presented data from the ARASENS trial. The study involved 1306 patients with metastatic prostate cancer (86% of whom presented with metastases and the remainder of whom developed mets while being followed after primary treatment). The trial evaluated whether adding the potent anti-androgen, darolutamide aka Nubeqa® (similar to enzalutamide and apalutamide) to standard ADT (e.g. orchiectomy, leuprolide, or other GnRH analog) plus docetaxel (Taxotere®) could improve survival. We already knew that 6 cycles of docetaxel added to ADT in this situation improved survival from the CHAARTED trial I wrote a blog about several years ago. This was the trial design:

The results of the trial were very positive and represent a new “standard of care” for patients with metastatic prostate cancer:

https://www.nejm.org/doi/pdf/10.1056/NEJMoa2119115?articleTools=true

Although it is too early to say whether some of the patients in this or similar trials, such as PEACE 1, have been cured, it is clear that throwing the “kitchen sink” at prostate cancer can offer real improvement in survival. Now the questions become: Who are the patients most likely to benefit? What kind of toxicities do these patients have to put up with? How much does this kind of treatment cost? What if we added other known effective treatments like Lu-177-PSMA or PARP inhibitors to appropriately selected patients? Would adding this kind of treatment cure some patients with oligometastatic disease? And perhaps most intriguing, could we imagine applying this kind of treatment to patients with newly diagnosed, localized (but high risk …e.g. Gleason 8,9,10, or node positive) disease as part of a plan that involved prostate surgery or radiation?

The answer to all of these questions will come only from appropriately designed clinical trials. I am reminded, too, of the famous quote from one of the pioneers in prostate cancer treatment, Dr. Willit Whitmore who said, “Is cure possible? Is cure necessary? Is cure possible only when it is not necessary?” There are obvious differences between the 52 year old man who presents with high risk prostate cancer and is otherwise healthy versus a 79 year old gentleman who had prostate surgery 15 years ago, a pacemaker, and now has a rising PSA with only one or two metastases showing up on a PSMA-PET scan.

The progress in prostate cancer research has accelerated dramatically during my career. As well, the costs of oncologic care are rising at a faster rate than can be maintained, “National costs for cancer care were estimated to be $190.2 billion in 2015 and $208.9 billion in 2020 (2020 U.S. dollars), an increase of 10 percent that is only due to the aging and growth of the U.S. population… National oral prescription drug costs were highest for female breast, leukemia, lung, and prostate cancers” (See this reference) As an aging (rapidly…) man myself, I can only hope we are able to fall back on the precepts taught in Sir William Osler’s essay, “Aequanimitas“, combining the qualities of “imperturbability” and “equanimity” to achieve “”coolness and presence of mind under all circumstances”. If so, we should be able to navigate the avalanche of medical knowledge and associated costs with compassion, empathy, and wisdom. Meanwhile, hats off to the researchers and men who participated in clinical trials and brought this advance and many others you can see here to fruition.

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January 22, 2022 · 6:23 pm

Keeping up…(or not)


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In my book club (all old men from various backgrounds – medicine, law, business, politics, academia, etc.) we read a book called “Artificial Intelligence: Confronting the Revolution“. In it, the author describes the various scenarios underway to deal with massive amounts of information. Far beyond Deep Blue, the chess computer that beat Kasparov in 1997, AI may help physicians of the future make great diagnoses and decisions and is already being tested in difficult settings like the early detection of pancreatic cancer.

Until then, for me at least, drowning in the information for oncology in general, and even just for prostate cancer is becoming daunting. Gone are the days when reading the New England Journal of Medicine would keep you abreast of the most important advances. This is a photograph of the journals that arrived just this week, all provided for “free” (and without my request) by the endless advertising in the first pages.

In “GU Oncology Now” there is a summary of important papers presented at the Society of Urologic Oncology 2021. For prostate cancer two papers on PSMA imaging and therapy (which I have covered elsewhere), one on racial differences and treatment patterns, and an ad for “why is precision medicine complicated in advanced prostate cancer?” (See the answer here) Hematology and Oncology covers “highlights from the 2021 European Society for Medical Oncology Congress and the 2021 AUA Meeting”. That one has 4 articles on darolutamide, 3 on enzalutamide, 2 on PD-1 inhibitor trials, and “meeting abstract summaries with expert commentary”. Scanning them, I find that for the most part I have already commented on many of them in this blog, so I move on to: This week’s NEJM. There, in looking at the table of contents, I find articles on diabetes control using “closed loop” glucose monitoring and insulin administration, use of oral microbiome therapy for c. diff infections, antibiotic prophylaxis for rheumatic heart disease, and one on 24 hour urinary sodium excretion and cardiovascular risk. Whew…nothing on prostate cancer –but wait, there IS one on an antibody drug conjugate for treating lung cancer…I wonder if it could have any role in the small number of prostate cancers that also have HER-2 mutations??

Oh, well, let’s move on… The Lancet Oncology has 12 original articles, 11 commentaries and 6 letters to the editor, and there are a couple of the letters that deal with prostate cancer from researchers I know personally. But wait – they are available online at “e7” and deal with “radiographic progression-free survival in the ACIS trial”. I already know about that since I was a monitor for that trial, so guess I’ll pass. That leaves JAMA Oncology. OMG! The first three articles I really do have to read. Here it goes:

  1. “Changes in Prostate-Specific Antigen Testing Relative to the Revised US Preventive Services Task Force Recommendation on Prostate Screening” This turns out to be an analysis of Blue Cross Blue Shield beneficiaries (some 8 million or so) aged 40-89 between 2013 and 2019. During that time, the USPSTF changed its guidelines from “not indicated” to “shared decision” and sure enough, PSA testing increased 10% among men 40-54 years old, 12% in those 55-69 years old, and 16% in the group least likely to benefit, aged 70 to 89. Hmmm.
  2. “Association of Treatment Modality, Functional Outcomes, and Baseline Characteristics With Treatment -Related Regret Among Men with Localized Prostate Cancer” Wow – I talk to men about treatment decisions like this almost every week. This one looked at 2072 men with localized prostate cancer diagnosed in 2011 and 2012, then analyzed in late 2020/early 2021, so almost 10 years of followup. The number of interesting observations in the 3 tables and 2 figures found in the article are too numerous to go over in this blog, but among them are more treatment regret among patients who received surgery or radiation vs those who chose active surveillance, less treatment regret in college or more graduates, and as expected more regret in men who had health problems related to treatment. But the concluding paragraph says it all:
    “The findings of this cohort study suggest that more than 1 in every 10 patients with localized prostate cancer experience treatment-related regret. A disconnect between patient expectations and outcomes, both as it relates to treatment efficacy and adverse effects, appears to drive treatment-related regret to a greater extent than factors including disease characteristics, treatment modality, and patient-reported functional outcomes such as urinary incontinence and other urinary symptoms, erectile dysfunction, or bowel dysfunction. Thus, improved counseling at the time of diagnosis and before treatment, including identification of patient values and priorities, may decrease regret among these patients.” I guess this validates the way I often end up my own counseling sessions: “Unfortunately, Mr. (and Mrs. in some cases) XYZ, there just isn’t any way to treat the prostate gland without causing some side effects.”
  3. “Outcomes of Screening for Prostate Cancer Among Men Who Use Statins”. This one is from Finland where we spent a lovely year on sabbatical in the mid-1980’s. My wife studied the Finns’ vaccination data for childhood meningitis, and I did a year in a molecular biology lab. We both were impressed with the Finnish Public Health system. The article utilized that system’s extensive database to evaluate the effect of statin use among 78,606 men who were part of a randomized study to evaluate PSA screening effects. The incidence of low grade (Gleason 6) cancers was reduced among the statin users, whereas detection of high risk cancers (Gleason 8-10) was similar. Buried in the data (3 figures, 2 tables) is a nugget. There is a trend towards decreased risk for all kinds of prostate cancer among statin “ever” users vs. non-users although no difference in mortality. Still…the study seems to support my bias that if tolerated (~5-10% of patients on statins develop muscle inflammation) most of my patients might benefit from being on statins.

Well, that’s it for this week’s journal arrivals. I won’t bother you with the 5-10 emails I scan every day from all sorts of “Web MD” and “Grand Rounds in Urology” places with even more to try and digest. How anybody can be a general medical oncologist these days and care for everything from lymphoma to breast cancer is truly amazing. Fortunately, there are expert resources like the NCCN Guidelines that are really helpful. Goodness knows we need them, and maybe AI will save us, but I’m not so sure.

Take a look, for example, at just the number of articles published so far in 2022 on statins and prostate cancer. Good luck 😁.

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July 28, 2021 · 2:18 pm

Cancer Camp and Survivorship


A cancer diagnosis affects every patient in a different way. However, regardless of what type of cancer is involved, it is a cold water “slap in the face” that we all share the same fate: “our days are numbered” – something everyone knows but we generally find it more convenient to simply not think about.

Prostate cancer, in my opinion, is somewhat different in this regard for most men. First, like all cancers, it is clearly a disease of aging, but even more so. The median age at the time of diagnosis is 66 years. This means the majority of newly diagnosed men have lived a reasonably long (and hopefully healthy) life. There has been time to deal with other health threats, watch children grow, and usually face the deaths of parents or close family members. However, the good news is that the vast majority of men will still have the opportunity for enjoying many more years of living.

Taken from the US SEER database: https://seer.cancer.gov/statfacts/html/prost.html

In fact, regardless of race or ethnicity, over 90% of men newly diagnosed with prostate cancer will be alive in 10 years. These data hold true even for men with regional disease, but fall off rapidly if metastatic disease develops. And there is continued improvement in treatment for the metastatic patients as well. In a recent article looking at three large studies for the benefit of second generation androgen receptor antagonists (enzalutamide, apalutamide, darolutamide) to delay metastases and improve survival, even men >80 years of age clearly did better than before.

From Lancet Oncology, July 23, 2021 https://doi.org/10.1016/S1470-2045(21)00334-X

So the question becomes, “what will you do with the time you have left?” regardless of how long that is. My thought, having just returned from volunteering at the Epic Experience cancer camp, is that it always good to take some time and reflect on how you want to spend that time. Write another paper? Start another company? Make even more money? Grasp for the latest treatment option? Or potentially reconsider family and friends and what really matters to you. The Epic organization has had trouble recruiting men to their camps, but for the men who have come, their perspectives have been altered in very positive ways as you will see in this video. Many more women come to the camps, just as women have led the way in advocating for breast cancer research, and in general reaching out via support groups. We have a lot to learn from them!

There are many support groups out there for prostate cancer survivors of all stages. Prostate Cancer Foundation has put a nice list together here. And if you would like online support for specific issues, Movember’s True North initiative has great articles to help you here.

The bottom line for me, having had a chance to “get back to camp”, is that we can all use a little encouragement to get out there and live again as we come out of our COVID isolation. I hope you will do just that this summer!

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June 16, 2021 · 2:01 pm

Lu-177-PSMA-617 and “what’s next?”


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The presentation that received the most attention from readers of this blog and the press at this year’s ASCO meeting was the one about Lu-177-PSMA-617 for patients with advanced, metastatic castrate resistant prostate cancer (mCRPC). I have previously posted about PSMA and this approach to treatment as you may want to review here. Briefly, Prostate Specific Membrane Antigen, is a protein expressed on the surface of prostate cancer cells. There are molecules (ligands) that bind to this protein and can be tagged with radioactive isotopes. Thus, the tagged ligand, once injected, carries the isotope to the tumor cells. If the isotope is a positron emitter, a CT-PET scanner (Positron Emission Tomography) will light up the tumor’s location. Examples include Ga-68 and F-18. If the isotope releases stronger radiation, (for example Lu-177 releases strong beta particles that can kill cancer cells, just as the approved agent, Radium 223 -aka Xofigo™ -is a bone seeking agent that seeks out bone metastases and kills cancer cells by releasing strong alpha particles) then prostate cancer cells expressing PSMA will be killed.

The data presented at ASCO 2021 on Lu-177-PSMA-617 was from a large phase III trial comparing Lu-177-PSMA-617 with “standard of care” in patients who had progressed on most other therapies. The results are shown in the following figure:

Slide from presentation on Cancer.net, 6/16/2021.

These data will be evaluated by the FDA and it seems likely this new therapy will be approved. The answer to the question of “what’s next?” for a new drug is usually to study its use in earlier stages of disease. What if patients who have metastases but have not yet been treated with hormonal manipulation were to receive the drug at the same time they start hormonal treatment? What if used before prostatectomy? There are 9 such ongoing trials you can read about here. The hope is, that by using the drug earlier, even more benefit will result, and this is often the case in cancer medicine – for example using early “adjuvant” chemotherapy in high risk breast cancer, or using apalutamide (Erleda™) at the outset when initiating prostate cancer ADT in high risk patients.

As we progress in our understanding of when and in whom to use more aggressive therapies, it will also be helpful to identify the patients at greatest risk for failing one treatment or another. In an article appearing this month in Annals of Oncology, investigators evaluated tumor DNA levels after a single cycle of abiraterone (Zytiga™) and found that patients who didn’t have circulating tumor DNA at the start or converted from positive to negative had significantly better overall survival than patients who did not convert to negative. This means that as soon as 30 days after starting abiraterone, you could already pick out patients in whom you might want to change therapy or add other agents to treatment. They also showed that patients with alterations in specific genes like TP53, RB1 or PTEN either at pretreatment or after one cycle had significantly shorter overall survival. This kind of individualizing risk analysis will further enhance the ability to introduce new drugs like Lu-177-PSMA-617 earlier in patients who need it and avoid toxicities in those who don’t.

For those who helped support my mustache during Movember, these findings are tangible evidence of real progress we can all be proud of. You can share in the great feelings and read about your accomplishment here: https://au.movember.com/story/new-treatment-for-men-with-advanced-prostate-cancer-more-effective-than-chemotherapy?tag=prostate-cancer. Our donations DO make a difference and thanks for your help!

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April 29, 2021 · 10:14 am

The Androgen Receptor (more than you wanted to know…)


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The treatment of prostate cancer by depriving the cancer cells of testosterone is now over 70 years old. Charles Huggins along with Clarence Hodges, a medical student at the time, discovered that by either administering estrogen (which will inhibit the brain from signaling the testicles to make testosterone) or surgically removing the testicles, patients with prostate cancer would have remissions, sometimes lasting for years. He received the Nobel prize in 1966 and there is a nice article reviewing the discovery and Huggins’ humility here.

Nothing much changed in prostate cancer treatment after that until the early 80’s when leuprolide, a peptide that could inhibit the signaling (like estrogen) from the brain to the pituitary entered the picture. This is the hypothalamic-pituitary-gonadal axis, and another Nobel prize was awarded to Andrew Schally for elucidation of the role of GnRH as the key hormone driving the system. (leuprolide is an analog of GnRH) Surprisingly, given the rapid development of anti-estrogens for breast cancer, truly effective anti-androgens took another 25 years or so to emerge. The past decade has yielded several new drugs that are now in standard use for prostate cancer as shown in the following table.

https://www.hematologyandoncology.net/files/2021/04/ho0421IsaacsonVelho-1.pdf

But blocking androgen synthesis by the cancer cells (abiraterone), or blocking the androgen receptor (all the other drugs listed in the table) kills most of the cancer cells, but not all. How do they survive? The answer lies, in part, in the complexities of the androgen receptor (AR) itself. This is where it gets really interesting (but probably more than you wanted to know).

In an absolutely superb recent review article, Velho and colleagues review how the AR works and drugs that are in development to block its activity when resistance to the above drugs develop. You need to download the PDF to see the figures, but this one illustrates the basics. Androgens get into the prostate cancer cell, then bind to AR, which then partners (dimerizes) with another AR molecule, and the dimer enters the nucleus of the cell and sits on specific genes, causing their expression. PSA is the gene you would know best, but there are many other genes that are activated, some of which lead the cells to divide or develop characteristics that lead to them metastasizing to lymph nodes or bones.

Testosterone (androgen) drives gene expression via the Androgen Receptor (AR)
https://www.hematologyandoncology.net/archives/april-2021/new-approaches-to-targeting-the-androgen-receptor-pathway-in-prostate-cancer/

The good news is that understanding how this system works has led to a wealth of drugs that can inhibit various steps in the AR pathway of cell/gene activation. These are shown here:

New drug categories being developed to block T (androgen) stimulation of prostate cancer.

Although the details are very complex, two of the more interesting approaches are bipolar androgen therapy (BAT) and the category shown as PROTACs. BAT consists of giving patients large doses of testosterone monthly while they remain on drugs like leuprolide to suppress the normal levels. In the recently published TRANSFORMER trial Denmeade and colleagues demonstrated that BAT was a better first choice in patients who had failed abiraterone when compared to the anti-androgen, enzalutamide. Further, BAT can re-sensitize some patients to abiraterone after BAT stops working.

PROTACs are drugs that can target various cell proteins for destruction by normal cell machinery. As shown in this figure, the proteasome is like a disposal that chews up proteins that have been “tagged” by attaching a protein called ubiquitin to them. Imagine that the green folded protein is the AR. If you can tag it, you will get rid of AR altogether, and that is what an experimental drug called ARV-110 does, attaches ubiquitin to the AR.

Folded protein could be the AR, and ARV-110 can lead to degradation of AR.

Ongoing clinical trials with ARV-110 have shown impressive PSA responses in a few patients who have been heavily pretreated and are resistant to all the other approved AR targeting drugs.

So, the good news is that there is still room for improving on treating prostate cancer patients with drugs that attack the testosterone axis, even 80 years after the first proof of principle was shown. However, it is also true that cancer cells are very “smart”, and can learn to survive via other cellular pathways having little to do with AR signaling. Other approaches, such as stimulating the immune system to recognize these cells is under equally intense study. If this doesn’t make you a believer in “science”, and a cheerleader for further investment, I give up! 😁

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January 13, 2021 · 7:08 pm

Pills vs Shots for Androgen Deprivation Therapy (ADT)


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My own interest in prostate cancer began with what, in retrospect, seems quaint and naive. When I arrived at the University of Colorado in 1978, as the first board certified medical oncologist, there were very few clinical trials underway. Having trained (at DFCI) with teams of researchers, my philosophy had evolved to the thought that “every patient should be treated on a protocol, and there should be a protocol for every patient”. This idea (in academic centers, at least) is how we make progress in treating cancer. I continue to urge every patient to participate in clinical research whenever possible, recognizing that for reasons of geography, convenience, or eligibility, it may not be possible. Clinicaltrials.gov lists all of the ongoing clinical research trials for patients and physicians, a dramatic advance in keeping everyone informed. You can learn how to use this tool in one of my previous blogs, here.

With few clinical trials going on at our cancer center, I wrote a naive letter to a number of pharmaceutical companies asking if they had any drug development trials that I might participate in. A single company, Abbott, wrote back inviting me to Chicago to discuss “Abbott 43-818”. This drug was an analog of gonadotropin releasing hormone, GnRH, a peptide (10 amino acids in this case) that looks like this: Pyr-{His}{Trp}{Ser}{Tyr}{Gly}{Leu}{Arg}{Pro}{Gly}-NH2. The 43-818 analog came to be known as leuprolide, and I had the opportunity to participate in taking it all the way from the first dose in men to a final clinical trial resulting in its approval as Lupron™. I’ve been caring for prostate cancer patients and doing clinical trials in prostate cancer ever since – fate!

The way Lupron™ works is shown in the figure below. Normally a part of your brain called the hypothalamus (1) releases a “pulse” of GnRH several times/hour. The peptide travels to the pituitary gland (2) and lands on cells called gonadotropins, causing them to release hormones LH and FSH that travel to the gonads (4) where the ovaries release estrogen or the testes release testosterone. Leuprolide interrupts this process by “over stimulating” its receptor on the pituitary cells and they turn off their LH/FSH production. Because of the small and relatively simple peptide sequence 100’s of other analogs have been made, and the molecular interactions with the receptor have been extensively studied. Some are agonists (like leuprolide/Lupron™/Eligard™, or goserelin/Zoladex™ and others are antagonists (degarelix/Firmagon™).

The hypothalamic-pituitary-gonadal axis

After a long research path, an oral antagonist (relugolix/Orgovix™) has now been synthesized, tested, and approved for treating prostate cancer. It is not a peptide, has the advantage of not having to be injected, and may be safer in patients with a cardiac history. The HERO trial evaluated 934 prostate cancer patients, 2/3 of whom received relugolix and 1/3 received leuprolide. As expected (based on the history of antagonists research), relugolix resulted in more rapid reduction in testosterone, faster recovery upon discontinuation, and faster reduction in PSA.

The frequency of the common bothersome side effects, hot flashes and fatigue, was similar. More patients on relugolix (12.2%) had diarrhea than those on leuprolide (6.8%). However, the leuprolide treated patients had more serious cardiovascular events (myocardial infarction, central nervous system hemorrhages and cerebrovascular conditions, or death from any cause), especially if they had a cardiac history. The incidence was 6.2% in the leuprolide group vs. 2.9% in the relugolix group.

All things being equal, use of relugolix would seem to be a superior choice for ADT in prostate cancer patients. However, as usual, “all things” may not be equal. First, while the biology above may seem to favor the antagonist, there are no data on whether this affects survival or time to progression of prostate cancer. The biology of reducing testosterone as the mainstay of treatment has not changed – we are attacking the same target: testosterone stimulation of prostate cancer cells. Indeed, the more rapid recovery of testosterone upon discontinuation of therapy (for example in a patient who receives several months of relugolix in combination with radiotherapy) might result in better quality of life with rapid recovery, but have a higher rate of recurrence due to the shorter overall duration of ADT treatment. Some patients will prefer pills to shots. On the other hand, insurance coverage for injections might be much better than that for an oral medication. The internet reported cost for a month of relugolix is reported to be $2313. The cost for a one month leuprolide dose is around $1700. However, the cost of a myocardial infarction is not insignificant, and thus comparison of one form of treatment vs another is always more complex than it initially seems.

I am writing this because I suspect there will be “news” articles and other advertising efforts for “Orgovyx™” in coming weeks/months and I hope to refer my patients to this article (and all the other ones I write). If a newly diagnosed patient has impending spinal cord compression, or major organ involvement or a history of cardiac disease, I would recommend the antagonist (relugolix/Orgovyx™) over the agonists (like leuprolide/Lupron™/Eligard™ or goserelin/Zoladex™). If a patient is already on one of those agonists, is doing well and has no cardiac history, there is probably no reason to change therapy. For a patient who is about to start therapy, I will discuss the options, and am happy to prescribe either an agonist or antagonist – it may well depend on insurance issues for a given patient. As with the Covid vaccine, the scientific progress in developing a non-peptide, oral agent is a testament to “our” (medical science) phenomenal scientific advances. The cost of such research (dating back at least to 2013 for relugolix) and what represents fair costs to patients or to Medicare and fair reimbursement to the pharma companies remain concerning to me.

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June 13, 2020 · 10:47 am

CAR-T and related immunotherapies


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One of your co-subscribers to this blog contacted me and asked if I would write a blog about CAR-T cells, and I have decided to include the closely related bi-specific antibody therapies. I am very intimidated by even attempting this, because the complexities of this field are daunting, so please do NOT show this post to your PhD immunologist cousin.

As most readers probably know, the immune system consists broadly of the “humoral” and “cellular” arms. When you get corona virus, (or any other virus) both arms are activated. Broadly speaking, your B-cells (lymphocytes that live in the lymph nodes and also circulate in your blood stream) make antibodies that attach to targets (“antigens” – in the case of corona virus, the spike protein you are tired of looking at on TV is the target antigen we hope a vaccine can be made from) and can inhibit the virus or can clear the antigen from your circulation. Antibodies consist of proteins (chains) that combine with each other and this is where things start getting VERY complex, but a single B-cell can make only one type of antibody (called a monoclonal antibody). Whether you know it or not, if you have an interest in prostate cancer, monoclonal antibody technology is “why you are here” – PSA detection was made possible by isolating a monoclonal antibody that would bind to Prostate Specific Antigen. But with modern recombinant DNA techniques, the chains that make up these antibodies can be combined in highly variable ways never found in nature. The history and complexity of the antibody story is illustrated here from this article. Screen Shot 2020-06-13 at 10.31.25 AM

The Y-shaped figure above is “an antibody” and the colored chains are the proteins in the antibody that can be extremely variable and give the antibody its ability to bind to any target. Note that the two arms of the antibody could be designed so that one arm would bind to one target and the other arm could bind to a different target. Voila! You could design one arm to bind to PSMA and another to a killer T-cell that would link a killer cell to your cancer cell.

Screen Shot 2020-06-13 at 10.42.33 AM

 This is the general idea behind an innovative cancer approach you may hear about called BiTE. In this figure, the working part of the tips of two “Y” antibodies have been linked and when injected into a patient, in theory the “killer” T-cell is forced to bind to the tumor cell via its “TAA” or tumor antigen. If you are a dedicated reader of this blog, you already are thinking about a great target antigen I previously introduced you to, PSMA. 

Now on to my VERY oversimplified description of CAR-T cells. The terminology refers to Chimeric Antigen Receptor – T cells. The science of these is related to the above description of antibodies in the following way: On the surface of the T-cells in your lymphocyte library is a completely different group of proteins that allow the T-cells to bind to and recognize antigens, much like the antibody system we discussed above. These proteins combine in chains on the surface of the cells to form “T-cell receptors”. Unlike the antibody system, their interactions with antigens are further modified by requiring recognition of “self”. Non “self” is why people who receive a kidney or heart transplant must receive drugs to suppress the immune system that will reject the transplant. Unfortunately cancer cells are mostly recognized as “self” so we don’t reject them. BUT… again using recombinant DNA technology, the T-cell receptors (TCR) can be re-designed so they DO recognize a tumor target, even though it is “self”. You can start with lazy, somewhat unresponsive T-cells that might be in the blood or even infiltrating a tumor, take them out, modify the receptor (dramatically as shown in the following figure), and force them to recognize a cancer, then re-infuse them into the patient like any blood transfusion.

Screen Shot 2020-06-13 at 11.02.34 AM

In the figure (taken from this article), the “antibody like” part of the receptor that controls “self” is CD3 and the “antibody like” part of the TCR receptor that binds to a tumor antigen or virus infected cell are the green proteins marked alpha and beta. The recombinant magic that is WAY beyond this blog is everything on the right. If you have the time and interest in really delving into CAR-T therapy for cancer, you really do have to read this article. But, for those who wonder “so why aren’t we doing this?”, the Cliff’s Notes answer is that (1) it is VERY expensive – each patient has to have his/her T-cells taken out and modified, expanded, then re-infused; (2) it has only worked well for blood cancers like leukemias so far; and (3) even though PSMA or some similar tumor target might be thought to be “tumor specific”, it turns out these targets are often expressed in low levels in places like your brain or lung. When the CAR-T cells begin attacking your normal tissues, you are in a world of hurt. If you have followed the COVID-19 story, you may have heard about the “cytokine storm” that is killing people by destroying their lungs. As you might imagine, combining these approaches with the other “hot” area of immunotherapy, the PD-1 inhibitors I have previously written about could make CAR-T treatment more effective but the toxicities even worse.

I hope this has been helpful and that your immunologist cousin or highly informed oncologist will forgive the effort to simplify a very promising but challenging field. I’m also grateful to the myriad of incredible researchers who have put this all together for us “cancer fighters” and their dedication is equally as worthy of honor as other warriors on front lines.

 

 

 

 

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May 10, 2020 · 7:53 am

COVID-19 and “the news”


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This won’t be a long blog, but since I anticipate lots of news this week regarding an article that was published a few days ago, I thought I would provide a “heads up” to my prostate cancer “groupies”. What makes the news and becomes “viral” is interesting and I haven’t had the opportunity to watch the sequence up close personally before. My wife is a pediatric infectious disease expert with specific interest in Kawasaki Disease. As you most likely have seen in the news over the past few days, SARS CoV2 now seems to trigger a KD type of illness in children. This became apparent a little over a week ago with calls flying back and forth from around the world among her friends, notably because Michael Levin, from London had seen some cases and sounded the alarm among the international colleagues. So, from “insider info” to public alarm seems to take about a week.

As you know from faithfully reading this blog, I predicted that men on androgen deprivation therapy might be protected from SARS CoV2 about 6 weeks ago and that physicians/scientists with access to large databases would be able to show this. And, true to the prediction, this past week an article appeared showing just that. I have summarized the data for you on this slide:

Screen Shot 2020-05-10 at 8.33.47 AM

It will be interesting to see this get picked up and “sensationalized” by the media over the coming days. And it is already underway. I am aware of a conference call with the CDC and another being hosted by the Prostate Cancer Foundation this coming week. So consider yourselves forewarned! CNN, FOX, ABC, etc. etc. will be all over it…

Now, as I also predicted, I would bet that there will be prospective studies looking at ADT as a form of therapy for COVID19 starting soon (if not already underway). My favorite design would be with the approved agent, remdesivir in a randomized prosepective trial. Male patients sick enough to be admitted to a hospital would all receive remdesivir, and 1/2 would receive ADT in the form of an anti-androgen (e.g. enzalutamide, apalutamide or darolutamide) or a single injection of a month of a GnRH analog like degarelix (Firmagon), or the androgen synthesis blocker abiraterone/prednisone (Zytiga). I would hope that this kind of approach could help men (and maybe even women) fight the virus by blocking TMPRSS2 as I previously showed you in the graphic on the original blog. Now YOU are the insiders!

PS, I think that another approach could be starting everyone in a nursing home “under attack” could be starting all the occupants on finasteride. Blocks DHT production from T and is very well tolerated in the  pcpt trial. Lower DHT -> lower TMPRSS2 -> lower viral replication.

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April 26, 2020 · 7:30 am

PSMA PET-CT scans for Prostate Cancer


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PSMA stands for Prostate Specific Membrane Antigen, which is a protein (enzyme) that is expressed on the surface of prostate cancer cells (and on a few other cell types). As with many cell surface proteins, you can find ligands that will bind to the protein, and then label these with radioactive isotopes that allow imaging. PET stands for Positron Emission Tomography, and of course, CT stands for Computerized Tomography. When you put these technologies together, you obtain a powerful way to look for prostate cancer that has spread outside the prostate gland. The physics of this (how a positron interacts with an electron, releasing gamma photons at 180 degrees) is very cool, but probably of interest only to the most nerdy. (I made a cloud chamber for my 7th grade science project and my hiking buddy is a nuclear medicine doc who wrote a definitive text on the math/science of his craft…so go figure).

Prior to developing PET agents for prostate cancer, we had standard CT scans and bone scans and we used these to determine whether someone with, for example, a very high PSA or high Gleason score had cancer deposits that had escaped (metastasized) from the prostate. If so, it was felt that putting them through surgery or radiation treatments in an attempt to cure was fruitless and exposed the patient to the unnecessary toxicity risks (impotence, incontinence, rectal damage, etc.) Especially if they had symptoms (e.g. bone pain), hormone treatment reducing testosterone was the best approach. If you had a rising PSA several years after local treatment, the question was always, “Where is the cancer?” but the sensitivity of routine bone and CT scans was quite limited not showing anything until the PSA reached 10 or so at which time ~1/2 of scans would be positive. Screen Shot 2020-04-26 at 7.26.14 AMThis figure illustrates the difference in sensitivity. A normal sized lymph node on CT scan (left) is revealed to  contain prostate cancer with the PET isotope technique (right). At present, the only approved PET scan in the U.S. is fluciclovine, the “Axumin” scan, which the FDA approved for detecting cancer in patients with rising PSA, but not in newly diagnosed patients. In several studies PSMA-PET CT scans are even more sensitive (about 3x) than Axumin. At the risk of calling up an overused phrase, “this changes everything”.

First, it is clear that many high risk patients we would previously have treated with surgery or radiation to the prostate hoping to cure them might now be found to have prostate cancer deposits outside of the treatment target (prostate or prostate + pelvic lymph nodes). A superb study in this month’s Lancet found that PSMA PET-CT scans provided higher sensitivity (85% vs 38%) and specificity (98% vs 91%) than routine bone and CT scans in high risk patients (PSA >20, Gleason 4+3 or worse). Does this mean we shouldn’t treat the prostate in high risk patients with positive scans? In the study, conventional imaging changed the management in 15% of men, while PSMA PET-CT imaging changed the plans in 28% (p=0.008). Should all high risk patients have a PSMA PET-CT before deciding on treatment? Should the FDA approve this scan quickly? (It is currently available only in research centers and not covered by insurance…read my blog on how to search for such studies or click here).

Second, what about treating a small number of prostate metastases (oligometastatic prostate cancer) in a patient who was treated years ago and now has a rising PSA? Ongoing investigations suggest this might delay the need for hormone therapy in such patients or potentially even cure some of them. But the PSMA PET-CT isn’t perfect. How high do you let the PSA go up before ordering such a scan? – the farther it rises, the more likely the scan will show something, but that gives the cancer more time to spread. A negative scan is no guarantee there aren’t many more foci of a few prostate cancer cells that will eventually show up elsewhere in the body. Is this some version of Whack-a-mole? And how do we define “cure” anyway?? (My personal definition is that you die from something else, regardless of your PSA or scan results).

Finally, since even at research centers the PSMA PET-CT scan may cost you $3,000 or so, is it worth it? It is “free” in the European health care systems, but we all know nothing is free – even if Medicare pays for something it costs society and ultimately must be accounted for in terms of value. Medicare covered PSMA PET-CT’s vs fixing pot holes and bridges? How about finding a treatment for SARS Co-V2 instead? No easy answers, but if you are like me, homebound as a “high risk” senior citizen, plenty to think about. Wash your hands, wear your mask, and enjoy your grandkids on Zoom!

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March 29, 2020 · 8:28 pm

COVID-19, ADT and Prostate Cancer


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Spoiler alert: As I start to write this, my intent is to delve into some basic science readers may find too detailed/complex and some speculation that has limited/no support and should NOT be taken as anything other than hypothesis generating. I fell in love with biology in about the 8th grade and with thinking about how to answer biology questions in medical school, so this is more self-indulgent writing rather than being written to inform.

Starting with the COVID-19 story, there have been so many excellent articles that if you haven’t read too many already, you can get a one minute overview from this video. Now for some more Screen Shot 2020-03-29 at 8.47.20 AMdetailed science. This figure from an excellent article in Science shows the real details of how the virus works and some of the drugs that might be useful in stopping or slowing it down at the cellular level. If you use your best “Where’s Waldo” approach, (and if you are an avid follower of prostate cancer biology) you may find a very familiar protein hiding in the membrane where the virus binds to the exterior of the cell, TMPRSS2. This protein is an enzyme in the family of serine proteases, proteins that can cut peptide bonds at the site of the amino acid serine. Trypsin is another example of this category of enzymes we use in the lab to release cells from petri dishes, and you use various enzymes every day in your dishwasher to digest proteins stuck to your dishes. As shown in the figure, TMPRSS2 plays a crucial role in the entry of the SARS-CoV-2 virus into the respiratory epithelial cells leading to COVID-19 disease.

I first heard of TMPRSS2 several years ago in a lecture at the PCF annual scientific meeting. Investigators at the University of Michigan found that in a large percentage of prostate cancer, the androgen response elements in DNA that control the expression of TMPRSS2 have become fused to an oncogene, ERG. Every gene in our DNA is controlled by “upstream” segments of DNA called promoters or enhancers that regulate the expression of the gene. In the case of prostate cancer the androgen receptor, AR, binds to testosterone (or DHT) and then the is translocated to the nucleus where it binds to DNA at the sites of androgen response elements, leading to transcription and expression of the “downstream” genes. A reasonable analogy is to think of testosterone flipping a light switch to “on” and the AR being the wire going to the light bulb, TMPRSS2, in our case. You are familiar with this if you know about drugs like Lupron, Zytiga, or Xtandi that block testosterone signaling in various ways. Although taking any of these drugs turns off many genes related to prostate cancer development and progression, one of these genes is clearly ERG (if you have the TMPRSS2:ERG fusion), and of course you probably turn down expression of TMPRSS2 in normal cells.

So what does this have to do with COVID-19? As you may have seen, men have approximately twice the mortality of women from infection with SARS-CoV-2. There are no doubt many possible reasons. Men smoke more. Men may not practice social distancing as much. Men have more heart disease. But what if one reason is that they express higher levels of TMPRSS2 in their respiratory epithelium? The exact mechanism of TMPRSS2 in the infection can be found in this article.  A cartoon from the article illustrates the several points in the viral infection cycle where TMPRSS2 (and other serine proteases) acts to facilitate the entry, replication and budding of the virion from a cell.

Screen Shot 2020-03-29 at 10.19.32 AM

The article discusses several drugs that are being investigated to inhibit TMPRSS2 that could hopefully be effective in fighting COVID-19. One of them, camostat (seen in the first figure in this post), is already scheduled to begin clinical trial at the end of this month.

However, there is already a very interesting global “clinical trial” underway if you have followed the above (and necessarily complex …sorry!) story about TMPRSS2. If ADT, familiar to all men with metastatic or high risk prostate cancer, turns down the expression not only of ERG and other oncogenic pathways, but also the expression of TMPRSS2, it might reduce the infection rate or morbidity/mortality from COVID-19. Looking at large global databases, it may be possible to see whether men with a diagnosis of both “prostate cancer” and “COVID-19”  can be extracted from the data, and then whether within this grouping, those men on ADT have a better outcome than those not on ADT. It would be complex, of course, since some of the men not on ADT might be on chemotherapy, or more sick in general, and thus more susceptible to dying from the infection. It might also be possible to see what the expression levels of TMPRSS2 in the pulmonary epithelium of men versus women are as a potential partial explanation of the differences in mortality. Finally, and this would be the most intriguing possibility of all, a clinical trial that combined some partially effective “drug X” from the list of drugs in the first figure with or without ADT could determine whether short term use of ADT could enhance the treatment. Proof that no one ever has a “unique” idea (and of the speed with which you can share ideas in today’s internet environment), in doing a minimal amount of literature research on this topic, I came across a preprint of a beautiful article looking at exactly the hypotheses I laid out above. It was submitted only 5 days ago! The authors have found very significant differences in the levels of expression of TMPRSS2 among adults using published databases and hypothesize that this could explain why some individuals may be more susceptible to bad outcomes. They also evaluate the potential of down regulation of the gene with ADT drugs like enzalutamide or estrogens and they conclude, “Together, these results identify existing drug compounds that can potentially be repurposed to transcriptionally inhibit TMPRSS2 expression, and suggest that the activation of estrogen pathways or inhibition of androgen pathways can be a promising modality for clinical intervention in SARS-CoV-2 infection.”

In summary, if you have prostate cancer and are on ADT, the well known side effects you put up with are unpleasant to say the least. But there is a “not-zero” possibility that your ADT is also protecting you. The best advice is still to practice social distancing, wash your hands, and be vigilant regarding your health, but maybe there is a silver lining in this story. I hope so, and there are already clinical and basic scientists exploring the hypotheses discussed above. Be well and my best wishes during these trying times!

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