ASCO: Preview of the Prostate Cancer Sessions

Today we’re speaking with Dr. Robert Dreicer, chair of the department of solid tumor oncology at Cleveland Clinic’s Taussig Cancer Institute. Dr. Dreicer will be discussing some of the prostate cancer highlights of this year’s upcoming American Society of Clinical Oncology (ASCO) annual meeting, held May 31–June 4 in Chicago.

-Interviewed by Michael Kaufman

Cancer Network: Thank you for being with us today, Dr. Dreicer.

Dr. Dreicer: You’re most welcome. I would characterize this year’s meeting as one in which there is a little bit of pause in the dramatic progress primarily in castration-resistant prostate cancer. The last couple of years have seen presentations at this meeting of basically phase III data about a whole host of new drugs, almost all of which have gone on to FDA approval-drugs like abiraterone (Zytiga), enzalutamide (Xtandi), and most recently radium-223 (Xofigo). This year, there’ll be a little less of that. However, I think that there will be certainly presentations made that begin to fill in the gaps as we move rapidly forward.

We’re going to see the results of a randomized trial testing the combination of either strontium-89 (which is a radiopharmaceutical) or zoledronic acid (a bisphosphonate) in combination with docetaxel. That’s a late-breaking abstract, so that data will be freshly presented at the meeting.

There’ll be a couple of other intriguing abstracts in terms of trying to augment our knowledge about this next generation of androgen receptor (AR) antagonists. Dr. Matt Smith from Massachusetts General Hospital, on behalf of colleagues, is going to present a trial of enzalutamide as monotherapy in hormone-naive prostate cancer patients. Now obviously enzalutamide has been approved in post-chemotherapy use for castration-resistant metastatic disease. This is a much earlier use of this novel AR antagonist, so I think that will be of interest.

Other things that caught my eye in terms of trying to understand some of the therapies that we’re using a little bit better-Dr. Chuck Ryan from the University of California, San Francisco, on behalf of his colleagues, is going to present a post-hoc analysis of one of the abiraterone phase III trials looking at the relationship of patients’ initial PSA and then subsequent decline, as it might predict for radiographic progression-free survival. This is in the pre-chemotherapy setting, and I think that again begins to fill in some of the gaps about trying to optimize which patients we treat, and predict who is likely to respond and who may have better durations of response.

Some other novel studies that are being presented-Dr. Howard Scher from Memorial Sloan-Kettering Cancer Center is going to report on some clinical biomarkers, things that include bone scan lesion analysis, which is a novel way to try to assess the level or degree of bone metastases in combination with circulating tumor cells and some other clinical parameters in a large phase II trial of cabozantinib, the drug XL184, a c-Met and VEGF inhibitor that’s in late stage of development in prostate cancer.

Other results that I think are interesting will be presented by Dr. Eric Klein from Cleveland Clinic. This is work done in collaboration with Genomic Health. They have a recently approved gene assay. The data they are going to present is actually somewhat provocative in that this test is based on being able to sample histopathology from either prostate cancer biopsies or prostatectomy, and trying to predict likelihood of disease progression. This data they are going to present would suggest that when you look at Gleason patterns 3 or 4-and because this is a clonal and heterogeneous disease, doing gene assays in the prostate has always been somewhat problematic-but they’re going to present data that suggests that they can genomically separate out 3s and 4s, meaning that whatever you see in pattern 3 or pattern 4 might be representative of the disease in and of itself. And this would be very important because then biopsies or sampling for genomic information would not be as dependent on where you stuck the needle or where you sample, so I think that’s also an interesting early piece of data that’s going to be presented.

I think in general that touches on some of the themes-again, filling in the gaps, biomarkers, and some novel therapy developments. But again, I think we’re in a bit of a pause between the rapid development of drugs and phase III data. So, over the next couple of years we’ll probably again see that move forward.

Cancer Network: Thank you very much for taking the time to speak with us today, Dr. Dreicer.

Dr. Dreicer: You’re most welcome.