Julie, do you think there will be any change in the treatment paradigm between docetaxel and abiraterone with this new update?
Julie Graff. I wasn’t that impressed by that study. I do not see it as practice changing, and it makes sense to me that the PFS is different in the 2 arms because we give chemotherapy and take a break vs giving abiraterone indefinitely. For me, there’s not really a shift.
Patients With Rising PSAs
Mark Klein. Let’s discuss the data from the recent studies on enzalutamide and apalutamide for the patients with fast-rising PSAs. In your discussions with other prostate researchers, will this become a standard part of practice or not?
Julie Graff. I was one of the authors on the SPARTAN apalutamide study.10 For a long time, we have had patients without metastatic disease but with a PSA relapse after surgery or radiation; and the PSA levels climb when the cancer becomes resistant to ADT. We haven’t had many options in that setting except to use bicalutamide and some older androgen receptor (AR) antagonists. We used to use estrogen and ketoconazole as well.
But now 2 studies have come out looking at a primary endpoint of metastases-free survival. Patients whose PSA was doubling every 10 months or shorter were randomized to either apalutamide (SPARTAN10) or enzalutamide (PROSPER11), both second-generation AR antagonists. There was a placebo control arm in each of the studies. Both studies found that adding the second-generation AR targeting agent delayed the time to metastatic disease by about 2 years. There is not any signal yet for statistically significant OS benefit, so it is not entirely clear if you could wait for the first metastasis to develop and then give 1 of these treatments and have the same OS benefit.
At the VA Portland Health Care System (VAPORHCS), it took a while to make these drugs available. My fellows were excited to give these drugs right away, but I often counsel patients that we don’t know if the second-generation AR targeting agents will improve survival. They almost certainly will bring down PSAs, which helps with peace of mind, but anything we add to the ADT can cause more AEs.
I have been cautious with second-generation AR antagonists because patients, when they take one of these drugs, are going to be on it for a long time. The FDA has approved those 2 drugs regardless of PSA doubling time, but I would not give it for a PSA doubling time > 10 months. In my practice about a quarter of patients who would qualify for apalutamide or enzalutamide are actually taking one, and the others are monitored closely with computed tomography (CT) and bone scans. When the disease becomes metastatic, then we start those drugs.
Mark Klein. Why 10 months, why not 6 months, a year, or 18 months? Is there reasoning behind that?
Julie Graff. There was a publication by Matthew Smith showing that the PSA doubling time was predictive of the development of metastatic disease and cancer death or prostate cancer death, and that 10 months seemed to be the cutoff between when the prostate cancer was going to become deadly vs not.12 If you actually look at the trial data, I think the PSA doubling time was between 3 and 4 months for the participants, so pretty short.