Category Archives: Targeted treatment

April 4, 2018 · 8:46 pm

Are we any closer to cure? (yes and no)


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I have at least three thoughts on the issue of curing advanced prostate cancer. First, the number of new treatments that are life prolonging has been incredibly gratifying. See my posts on abiraterone, enzalutamide, apalutamide, Sipuleucel-T, and Radium 223, to say nothing of cabazitaxel and docetaxel. That said, my second comment (and yes, I DO say this in the clinic to try and keep some perspective on a deadly, but often slow disease) is that “if you die of a heart attack or a stroke, we call that a CURE!” Many patients have very slow moving prostate cancer that just grows old with them, and some of the drugs listed above can slow it down still further, even though the side effects (particularly of ADT itself) are definitely unpleasant. The third thought is an old saw: “For every complex problem, there is a simple answer, and it is often wrong.” I looked it up, and it is attributed to H.L. Mencken, who actually said, “Explanations exist; they have existed for all time; there is always a well-known solution to every human problem — neat, plausible, and wrong.”  I found he also said, “We are here and it is now: further than that, all human knowledge is moonshine”. Pretty cynical, but we digress…

Thus, the article that made me think about how complex a problem prostate cancer actually presents us was this one. The authors are very much the Who’s Who of prostate cancer research, and what they did was sequence the exomes from 1,013 prostate cancers. They were looking for so called, “driver mutations”, that is, mutations in a gene(s) that are the underlying cause, or at least the accelerators of prostate cancer. Their abstract conclusion states, “We find that the incidence of significantly mutated genes (SMGs) follows a long-tail distribution, with many genes mutated in less than 3% of cases. We identify a total of 97 SMGs, including 70 not previously implicated in prostate cancer…”

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The list of mutations found

This means that although we might see some drugs developed for the most common mutated driver genes, there lurks a host of others for which developing a drug for the very small number of patients (even if that is possible – not all mutated genes are “druggable”) with a given driver may not be economically attractive. And then there is the issue that if one of the common driver pathways (for example the androgen receptor) is effectively knocked out, as has been done with the second generation inhibitors, it is likely there are other mutated drivers in the wings. 

On the other hand, the study of metastatic prostate cancer has uncovered a wealth of new genomic classifiers that may be of real utility in further separating the “bad” cancers from the more indolent variety. As they state, “this analysis, which includes more advanced cases, has identified new and biologically and clinically relevant events and creates an opportunity to prospectively assess a metastasis-associated genomic marker for clinical stratification in localized prostate cancer.” All well and good, but don’t forget the issue of tissue heterogeneity. If you biopsy one metastatic site, or even one site within the primary tumor, you might get a different answer from a site only a few millimeters away or from a different metastasis, as I previously pointed out in another very sophisticated article by some of the same authors.

Nevertheless, be of good cheer. To have so many outstanding biologists and physician scientists uncovering the underlying mechanisms of prostate cancer is a good thing. The more we learn, the more opportunities we have to slow the disease down, even if there may never be a “cure” other than a heart attack. Immortality may be elusive, but your friends and family are not…carpe diem!

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January 10, 2018 · 2:25 pm

Of Prostates and Teslas


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If you thought this might be an article about how your urologist shops for his/her newest fancy car, you are mistaken (sadly…). Nikola Tesla was a fascinating inventor and ultimately “mad scientist” at the turn of the last century. Every time you plug your cuisinart into the wall to chop something up, you are the beneficiary of his contributions to the alternating current coming to your kitchen and the motor driving the chopper. My favorite story (because of the local connection) was his laboratory in Colorado Springs, where he attempted to develop a method of transmitting power without wires. By creating YUUUGE electromagnetic fields, he could make lots of electrical things happen at considerable distances, including knocking out the power station for the city. Here’s a quote from the Wikipedia article:

He produced artificial lightning, with discharges consisting of millions of volts and up to 135 feet (41 m) long.[11] Thunder from the released energy was heard 15 miles (24 km) away in Cripple Creek, Colorado. People walking along the street observed sparks jumping between their feet and the ground. Sparks sprang from water line taps when touched. Light bulbs within 100 feet (30 m) of the lab glowed even when turned off. Horses in a livery stable bolted from their stalls after receiving shocks through their metal shoes. Butterflies were electrified, swirling in circles with blue halos of St. Elmo’s fire around their wings.[12]

Of course, for purposes of this blog, the key thing is that the strength of magnetic fields was named after him. When you get an MRI of your prostate, brain, or anything else, you are put into a machine with a superconducting magnet that produces 1.5 or 3 “T” of strength. At the risk of being completely wrong and oversimplifying, what happens in the MRI machine is that a strong magnetic field temporarily lines up the hydrogen atoms in the water that is 70% of “you”, and when these atoms “relax” they give off radio signals that can be converted to images. Details and images are here. Early on, my colleagues and I were fascinated by the possibility of using MR to investigate the prostate gland and published an article (completely ignored – cited only 3 times, so must not have been that important…) showing changes in MR that occurred after testosterone administration to castrated rats.

Now there are complex MRI protocols to image the prostate using techniques I don’t fully understand (multiparametric imaging) that give us remarkable pictures of the prostate gland. Here is one:

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Prostate gland with red arrow indicating a suspicious lesion that could be biopsied or followed closely.

As with any radiologic imaging technique, the skill of the radiologist as well as the equipment being used determine the accuracy of the MRI to diagnose a cancer.

While most of us learned how to “read X-rays” in medical school, it is beyond most clinicians to read MRI’s of the prostate. Fortunately, the radiologists have developed a system that helps us think about “how abnormal” some area of the gland is, called PI-RADS.  This can be very useful in thinking about what area to concentrate on when biopsying a patient, or in trying to determine whether surgery or radiation therapy should be altered if there is concern that the cancer is outside of the gland. An interesting question that is still controversial is whether the MRI could replace repetitive biopsies in a man who has chosen active surveillance. Particularly when combined with molecular techniques (see my previous blog here) to characterize biopsies, it may be that Tesla will be helping to do more than get you from one place to another or run your electric shaver. (Rock on, Elon Musk) To me, that is a pretty interesting outcome from knocking out all of the lights in Colorado Springs!

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November 24, 2017 · 10:50 pm

23 & You – Genetic tests for pca


The genetics of prostate cancer are daunting, but there are now a range of tests available that could be used at almost every stage of the disease IF you can deal with the answers you are likely to receive. Generally these tests are the product of science that goes something like this: A complete molecular picture is taken of all the mutations or all the genes expressed in a series of prostate cancer patients diagnosed years ago. For these patients “all you need to do” is go back to the paraffin blocks that were saved for each patient, extract the DNA/RNA and quantify gene expression and any mutations that can be detected. A decade ago, the technology for doing this was daunting, but now it is relatively easy. Once you have the gene expression profile, you can ask a computer to look for gene expressions that correlate with a certain outcome. For example, you take 500 patients from one center for whom the outcome is known…50 patients are dead, 32 from prostate cancer…70 patients developed metastases by 5 years…these 315 patients are alive and well with no evidence of recurrence…etc. Let’s say there are 50 genes that show changes in expression or mutation. Do we need all 50 to forecast what happened to the patients in that group? No. A computer algorithm can keep testing combinations and permutations of genes and reduce the 50 to a smaller number. We can either let the computer pick the final genes, or we could start with genes we think are related to tumor progression and then do the reduction. In the end, we have a small number of genes with characteristics that accurately separate the patients into “good” and “bad” groups and everything in between. We now take our gene panel, reduced to something like a computer chip and apply the test to 500 patients at another institution blinded from what actually happened to those patients. If our algorithm works, we should be able to accurately predict what happened to those patients in the next 5 or 10 years. If it works, our testing system has been validated, and we can begin offering the test to newly diagnosed patients at some stage of illness. For example, a Gleason 3+4=7 patient might fall into a group where surgery produced a 90% chance of being cured at 10 years, or a 40% chance depending on the gene expression. BUT…and this is key…what to do about the result is still a complex decision for both patient and physician. If you are a Gleason 3+3=6 patient and with no treatment at all you have an 85% chance of “cure” at ten years, is that good enough? What if it is a 95% chance? Will that make you more comfortable choosing no treatment, or do you want to be cured at any cost (impotence, incontinence, other side effects of radiation or surgery)?

As none of these tests has been proven in a prospective study – that is, using the tests to do something like even more aggressive therapy in a group of high risk patients, we are still in the early stages of understanding how and when to use them. Fortunately, my colleague, Dave Crawford and some colleagues have put together an excellent website to help patients/doctors understand the tests. http://www.pcmarkers.com has a list of most of the available tests and you can see what results might look like before you and your physician decide to send one off. This is a rapidly evolving field however, and not every test that is being commercialized is listed, and at big centers, there are always new tests being developed.

Finally, as with all of medicine, the payment systems/insurance coverage is crazily complex. Only today, I received an email with the “news” that a cardiologist/congressman, Rep. Buchson has introduced a bill called the “Prostate Cancer Misdiagnosis Elimination Act of 2017” that uses DNA profiling to make sure the tissue being tested is yours. You could theoretically apply this test to ANY cancer biopsy of course, so why prostate cancer? Then there is the motivation…call me cynical, but I suspected that the good congressman, meddling in medicine, might have a local connection, and sure enough, the company that markets the test is from his home state, Indiana. Not to say it isn’t important to know that tissue being tested comes from the correct patient or that the test isn’t a nice application of the kind of technology that identified OJ’s blood, just that we live in interesting times where medical technology is rapidly consuming more and more of our tax/insurance/personal dollars. Personalized medicine will depend totally on this type of technology and can be incredibly expensive. Whether it saves money or consumes it may depend on how many “worthless” (for that patient…and is a treatment with only a 5% chance of working really worthless??…not if you are in the 5% group) treatments are avoided and at what cost. I don’t have the answers. Hopefully this blog at least helps you begin to understand the current molecular diagnostic landscape.

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June 5, 2016 · 7:52 am

Precision medicine and AR-V7


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Much of the news this week in prostate cancer will be generated by the annual ASCO Meeting in Chicago where VP Joe Biden will be speaking tomorrow about the moon shot. It will be hard to miss the excitement – perhaps even eclipsing (for a day or so) the ongoing circus that is our presidential politics at the moment.

In prostate cancer, there are likely to be considerable news releases regarding precision medicine, and especially AR-V7, so I thought I would explain this a bit. Precision medicine is the broad terminology that (in oncology) refers to looking at the individual patient’s tumor genetic profile. In the broadest sense, it can also refer to all of our genetic makeup that can influence, for example, how we metabolize drugs. The optimal dose for you might be different from that for me based on our inheritance of slightly different enzymes that are involved in breaking down a certain drug. In oncology, it is now possible to perform whole exome sequencing (WES) on circulating tumor cells that give a nearly complete picture of an individual’s cancer – what is driving it, and what it might be susceptible to. In metastatic prostate cancer, as you know from my previous post, the tumor cells circulating in the blood stream could be coming from a variety of places, and likely each individual cell might have slightly different genetics – creating a considerable challenge in the long run for picking out “the” drug that is best for that patient, even with this high-tech approach. Nevertheless, WES has already demonstrated exceptional ability to find targetable mutations in cancer cells, often with several different pathways of potential susceptibility in each patient. Two challenges arise: 1) the drugs that target each “driver pathway” are often frightfully expensive, and 2) which one or ones would be the best to target?

So what about AR-V7? 14 of the 214 prostate cancer abstracts (keep that in mind when you ask your doctor, “Hey doc, is there anything new out there?”) deal with this biomarker. AR-V7 stands for Androgen Receptor – Splice Varient 7. I know…”too complicated for me to understand”. Think of it this way: The AR is the energizer bunny, and testosterone is the battery. Put the battery in the bunny, and he hops into the nucleus of the cancer cell and turns on all sorts of genes (including psa) that drive the cancer cell to do bad things (divide, invade surrounding tissue, metastasize, etc.). Now suppose the bunny becomes autonomous – no need for a battery – he can hop in and do his thing whether or not testosterone is present. This means that all of the new treatments that target testosterone (abiraterone/Zytiga™, enzalutamide/Xtandi™, etc.) really won’t do much. We call this resistance. Castrate resistant prostate cancer (CRPC) used to mean “simply” tumor progressing in spite of very low levels of testosterone (achieved with drugs like leuprolide/Lupron™, goserelin/Zoladex™, etc) or T-blockers like bicalutamide/Casodex™. What we now know is that patients whose cancers are expressing the AR-V7 form of the AR will not respond well to any of these drugs. This means that it could make more sense to proceed directly to treating with chemotherapy with a drug like docetaxel/Taxotere™. Dr. Scher and colleagues at MSKI report in this weeks JAMA Oncology and at the ASCO meeting on the utility of looking for AR-V7 in circulating tumor cells to guide therapy. Screen Shot 2016-06-05 at 8.21.17 AMUsing special immunofluorescent stains, they can identify the “bunny” (shown in white on this photograph from their publication) in the nucleus of some cells in some patients, and these patients are better treated with chemotherapy than with approaches targeting the AR. The implications of this are that we may be able to use such tests to avoid the expense and wasted time of trying to use AR directed therapies in some patients. As often happens, the science is far ahead of the insurance companies however. The Hopkins group have commercialized the test and in an abstract show that it can be cost effective in populations of patients where AR-V7 is likely to be >5% prevalent. Better yet, these insights are now in clinical trial to hopefully develop new treatments for these patients such as galeterone, which may be able to degrade (“kill”) the bunny as described in this abstract from the ASCO meeting.

So YES, we are making progress, and there is a LOT that is new “out there”. Scan the abstracts for yourself – it really isn’t that hard – and kudos to the prostate cancer researchers who are moving this fight forward so quickly.

 

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February 2, 2016 · 9:33 pm

Olaparib for resistant prostate cancer


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In what is the first (and hopefully one of many) example of using modern genomic methods to match treatments to the molecular defects in prostate cancer, the FDA has just granted “breakthrough designation” to olaparib, a drug made by AstraZeneca. This followed a publication in the NEJM with nearly as many authors as patients, illustrating the power of team science and international collaboration.

Cancer cells develop numerous mutations that provide them with the ability to divide, metastasize, escape immune surveillance and so forth. One of the drivers of this mutation cascade is genetic instability, in part due to the accumulation of mutations that keep the cells from correcting DNA alterations. These mutations in DNA-repair enzymes can leave the cancer susceptible to additional inhibitors of DNA repair, one of which is PARP, an enzyme found in the nucleus that detects DNA strand breaks and initiates repair. When olaparib interferes with this enzyme, cells can become so genetically unstable they die.

In the TOPARP-A trial, 50 patients who had castrate resistant prostate cancer and had progressed on second generation anti-androgen treatment and docetaxel were given olaparib. 16 of 49 evaluable patients responded, however the exciting finding was that because these patients participated in the clinical trial and allowed the investigators to biopsy their tumors, it was possible to relate response to the presence of defects in the DNA repair genes. For this subgroup, 14 of 16 responded, indicating that using the repair defects as a biomarker you could predict high response rates, while at the same time, patients without such genetic defects had a much lower response rate (2/33). There is an excellent video that illustrates the results accompanying the publication that you can find by clicking here.

Although this is terrific news for prostate cancer patients, it brings a number of challenges. Testing for genetic mutations is a growing (and somewhat expensive) process. When compared to giving patients a drug that predictably won’t work, however, it can be very cost effective. Second, when you biopsy a tumor, the results can vary depending on where you biopsy as I discussed in this previous blog. “Liquid biopsies” of circulating DNA or tumor cells may provide some help in meeting this challenge.  Third, responses to targeted therapies such as olaparib tend to be rather short-lived, as the cancer cells continue to mutate to find ways around the new agent. The hope would be that combining a targeted treatment like olaparib with an immune approach might bring more prolonged responses. Finally, we must find a way to deal with the extraordinary costs of the new oncology drugs. The actual cost of olaparib is $13,440/month according to this article in the ASCO post. I have previously opined on this issue and invite you to join the discussion by clicking here.

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