Rick Baehner, MD, Chief Medical Officer, Precision Oncology at Exact Sciences, discussed a study on the Oncotype DX® Genomic Prostate Score (GPS) test, the only genomic test for prostate cancer with 20-year outcomes, in assessing the risk of long-term distant metastases (DM) and prostate cancer-specific mortality (PCSM) for patients with localized prostate cancer.
DocWire News: What prompted you to undertake this study?
Dr. Baehner: Well, we wanted to understand the GPS and its association with long-term outcomes. So we wanted, in particular, to understand, does the GPS predict the risk of recurrence prostate cancer metastasis, as well as prostate cancer-specific death over the 20-year period?
DocWire News: What are some of the key takeaways from this study?
Dr. Baehner: Some of the key takeaways with this study are, like we reported, now, eight years ago, when we developed the GPS score, that now at 20-year follow-up, the GPS appears equally associated with the risk of prostate cancer metastasis and prostate cancer death. And what this means is prostate cancer is a type of cancer that can take many years in those few patients who will experience distant metastasis for those to occur. So we really wanted to understand the association between the GPS, which measures gene expression, and its ability to predict late recurrences, that is metastasis or prostate cancer specific death, at a long time period. And that’s what we’ve done in this study at 20 years.
DocWire News: Did any of the study’s findings surprise you?
Dr. Baehner: It didn’t. One caveat about this study is that we did use this cohort with Cleveland Clinic and with Dr. Eric Klein to select the genes for the GPS study. So we selected those when the patients had 10 years of outcome. And the question we now wanted to ask is are these genes equally informative now that there’s 20 years of outcome data? And the answer is yes they are. So that’s always a good surprise when they remain predictive. And in this case they were.
DocWire News: What limitations did the study have?
Dr. Baehner: That’s a great question. And I think I did allude to one of the questions or one of the points. And that is that the signature was developed in these patients. This is 400 plus patients that represent a cohort sampling of several thousand patients at the Cleveland Clinic. We did the gene identification in this cohort. And then for this study, we analyzed the index lesion. That is the lesion that had the highest prostate grade in these samples. And the fact that these were used for the algorithm development is a limitation of this study.
DocWire News: Do you have any future research plans pertaining to this area?
Dr. Baehner: We do. The GPS score, the Oncotype GPS score, is a score that is able to predict not only prostate cancer metastasis and prostate cancer death, but something called adverse pathology. When a urologist wants to put a man who has earlier stage prostate cancer or localized prostate cancer on active surveillance, they want to be sure that they are not missing any phosphite of disease that could be of a higher Gleason score or Gleason grade group of three or higher. They also want to make sure that the prostate cancer is not invading through the capsule or into the seminal vesicle. And that triad of features, a higher grade, extracapsular extension or seminal vesicle invasion is known as adverse pathology. And so adverse pathology is an intermediary between the standard factors, like grade, and the hard end points, like prostate cancer metastasis and prostate cancer death.
So we will be doing work with this cohort to show the correlation between men who were found to have adverse pathology, either this tumor growing out of the prostate or into the seminal vesicles, or have a higher Gleason grade, in its association with prostate cancer metastasis and prostate cancer death. And we’re looking forward to publishing that later on this year.
DocWire News: Any final thoughts you’d like to share?
Dr. Baehner: I think that perhaps the most important finding from this study is that now the GPS score is now really the only score that has been demonstrated to be associated with this adverse pathology and the hard end points. And particularly now, prostate cancer metastasis in death at 20 years. And that’s a very important finding. Many patients diagnosed with prostate cancer will have this disease for many years. And understanding the ability of the score to predict metastasis and death is extremely important.