David I. Quinn, MD: Circulating Tumor Cells and Prostate Cancer from ASCO 2011
David I. Quinn, MD is Associate Professor of Medicine at University of Southern California (USC) Keck School of Medicine and the Medical Director, USC Norris Cancer Hospital. Dr. Quinn discusses the role of circulating tumor cells for prostate cancer treatment at ASCO 2011.
The Group Room at the 2011 American Association For Cancer Research Annual Meeting was made possible, in part, by:
VIDEO TRANSCRIPT
Selma R. Schimmel, Founder & CEO, Vital Options International:
This is Selma Schimmel at ASCO 2011 in Chicago and we’re talking to physicians here about the latest research in clinical advances across many different cancer types. And now we’re joined by one of The Group Room favorites, Dr. David Quinn: Medical Director, USC Norris Cancer Hospital, leader of the Developmental Therapeutics Program and Head of Genitourinary Oncology, all at USC where you’re also an Associate Professor amongst other things, at the Keck School of Medicine. Thank you. And today we’re going to talk about all kinds of things as it relates to the prostate. So, Dr. Quinn, as with breast cancer, where I remember there was lots of research going on in looking at circulating tumor cells, now I’m reading about circulating tumor cells when it comes to prostate cancer.
David I. Quinn, MD, Medical Director, Norris Cancer Hospital, USC:
Correct. So, I think we had some really interesting stuff generically on circulating tumor cells this year when a number of publications on breast and colon cancer came out in the Journal of Clinical Oncology. And there was a very interesting accompanying editorial, which stated something like, ‘not all circulating tumor cells are bad, not all circulating tumor cells are good’ and it implied that we have a lot to learn, and we do. What we know, at this point, and what we’re going to see from Dr. Howard Scher’s presentation – Dr. Scher is from Memorial Slaon-Kettering in New York – he’ll present some data, from the Abiraterone 301 study; those are patients that went on to Abiraterone who previously had Docetaxel chemotherapy.
The study showed a significant survival advantage for the administration of Abiraterone with Prednisone compared to Prednisone and led to the recent license of the drug by the FDA and we’re actually able to prescribe it. So, we have many patients in the United States receiving the drug now. Now, the issue in this study was they collected circulating tumor cells before they treated the patients and at sequential times after treatment. The data will show that if you have an elevated circulating tumor cell that’s more than five in a blood sample taken before you start, that your prognosis is worse. So, you have more, you don’t do as well overall. The study will also show that your prognosis is improved if on Abiraterone treatment your cells fall below that level of five. And we have these data or comparable data from a number of sets now and they are being compiled and put together so the FDA can look at them to see whether they’re the sort of surrogate that we might use that will help us manage prostate cancer.
This could be a new bio marker. So, telling early whether you’re responding to one of the chemo therapies or one of the hormonal therapies that we use in prostate cancer would be very worthwhile, and it would be nice if this were a universal surrogate. The problem is that we’ve used PSA to do this for some years and the FDA has not accepted a PSA in the serum or changes in PSA in the serum as a surrogate that we could use as a clinical trial indicator. And our hope is that our change in circulating tumor cells may allow us to move towards that.
Selma R. Schimmel:
What volume, before it’s measurable, in one’s blood?
David I. Quinn:
Right. Well, it varies from cancer to cancer and from person to person. And it’s actually a very good question. So, we take seven and half milliliters of blood, it’s about a standard blood sample, just from the vein like when you’re having a normal blood test, like PSA testing and… which is usually done at the same time. We actually run this through a series of fairly complex filters. The later your disease, the more metastases you have, generally, the more cells you’ll have circulating in your blood that are distinct from blood cells. They have what we call epithelial characteristics and these are picked up by a variety of techniques.
The one we have at the moment, which is run by a company called Veridex, which is part of the Johnson & Johnson conglomeration, it detects epithelial cells and counts them. But most of the patients that we look at and have metastatic disease actually don’t have detectable cells. So, it’s not useful in everybody, and in fact, there’s only a small number of patients that it might be useful in. And if you start with an undetectable level, then following the circulating tumor cell levels has a questionable benefit, and it obviously entails a cost. We know that in the studies done of falling circulating tumor cells, from about five to below seems to be important, it predicts survival.
In terms of looking at an increase in cells, whether that predicts survival, in other words, you need to switch therapy because this isn’t working and you need to look at something else to try and control your cancer- we haven’t quite reached that level yet. And the other issue about numbers is, we’re looking at relatively small numbers of cells in the blood. So, you look at five; well, the relative number of blood sample or blood cells – red cells, white cells and platelets – and that sample’s got a number in the millions. So, we’re looking at a level of detection of like a needle in a hay stack.
It’s clear that there are other cells there that are circulating from the tumor, epithelial cells from what you’d think is the tumor itself, endothelial cells from the blood vessels in the tumor, and then some other cells that stick epithelial cells and other cells together, called mesenchymal cells, also circulate; what we call the circulating microenvironment. So, what we’re going to see in coming years, and we have a number of presentations here this year that are touching on this, is a better way of looking at these circulating cells, the circulating microenvironment. And our hope is, that is a research tool that will allow us to evaluate the tumor without having to do a biopsy. Prostate cancer is usually in bone, that’s not easy to do all the time… to teach us some things beyond just the numbers. And I think our sensitivity in counting the numbers will improve. And the Veridex assay hopefully will be improved, that they’re partnering with some people at Harvard and there are a number of other groups, including our group at USC that are working hard on this to try and improve that technology.
Selma R. Schimmel:
Thank you, Dr. David Quinn, Medical Director, USC Norris Cancer Hospital, Leader of the Developmental Therapeutics Program and Head of Genitourinary Oncology.
David I. Quinn:
Thank you, Selma.
Selma R. Schimmel:
And best friend to The Group Room.
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