PARP Inhibitors in Prostate Cancer - Episode 7

Routinely Ordered Testing for Metastatic Prostate Cancer

Alicia Morgans, MD, MPH, explains the different testing that should be done when being diagnosed with metastatic prostate cancer.

Matthew Fowler: Hello, and welcome to this CancerNetwork® OncView program titled “PARP Inhibitors in Prostate Cancer.” I’m Matthew Fowler, an editor with CancerNetwork®. We have with us today Dr Alicia Morgans, a genitourinary medical oncologist and the medical director of the survivorship program at the Dana-Farber Cancer Institute in Boston, Massachusetts. Thank you for joining us today, Dr Morgans. Let’s get started.

Alicia Morgans, MD, MPH: Thank you so much. I’m happy to get started.

Matthew Fowler: Let’s first look at diagnosis and testing in prostate cancer. What testing do you routinely order for a patient with metastatic prostate cancer?

Alicia Morgans, MD, MPH: That’s a great question. It’s an answer that has evolved over the last few years, so it’s important to make sure we know the most updated guidelines. At this point, for any patient with metastatic prostate cancer, it’s encouraged and recommended that we get germline genetic testing, and to ensure that this is done as soon as we meet the patient, because this could have potential therapeutic options for the patient himself in the future but also implications for his family members at the time of initial testing. Germline testing is done by blood sample, or sometimes by buccal swab, which is saliva testing. This is something we’re going to want to do as soon as we meet the individual.

Some people have concerns about whether they have genetic counselors to follow up on those results, so that’s something to think about. There are online supports associated with the germline genetic testing companies so that if your practice doesn’t have the ability to do genetic counseling on the back end for patients who have evidence of some of these cancer syndrome–associated mutations, you can always engage with the company that has those support systems in place.

In addition to that, for patients who have metastatic disease, it’s recommended that we consider somatic testing as well. This will give us twice the number of patients who may be eligible for ultimate treatment with targeted therapies like PARP inhibitors. Also, importantly, things like MSI [microsatellite instability]–high and TMB [tumor mutational burden]–high status are identified only on somatic tissue testing, or sometimes in some circulating tumor testing. It’s important for us to make sure we’re looking for that, because for the 1% to 3% of patients who may have MSI-high status, the treatment, pembrolizumab, can be extremely effective. But we won’t know that this is an option unless we do the testing.

Matthew Fowler: Let’s look at the time frame of this. When do you typically order testing? Is that at the initial diagnosis, upon progression or recurrence, or both? Is there a set timeline that you have?

Alicia Morgans, MD, MPH: For germline testing, it’s as soon as a patient has metastatic disease. For patients who have high-risk and even intermediate-high-risk localized disease, urologists or potentially radiation oncologists involved in the care may also order germline genetic testing. But for any patient with metastatic disease, the first time I meet him, I try to talk about getting germline testing.

Somatic testing can be more variable, and that can depend on an individual clinician and his or her workflow, but it’s necessary for treatment decision-making when we think about patients in the mCRPC [metastatic castration-resistant prostate cancer] space. By the time a patient has mCRPC, we absolutely need to think about it. If it works better in the workflow to do that tumor tissue testing or metastatic site testing earlier on, so you have that information when the patient progresses to mCRPC, that’s a good way to go too. It depends on the patient, the clinical workflow, and what you’re going to do with the information on the back end when you might use those treatments.

This transcript has been edited for clarity.