It’s difficult to know what to make of that information because, as we’ve discussed already, there are other systemic therapy options that are being used more and more upfront such as abiraterone. Can you see the same benefit of radiation in that setting? The flip side is that in this study, radiation just targeted the prostate; could survival be improved even more by targeting all sites of disease in patients with oligometastatic disease? These are still open questions in prostate cancer and there are clinical trials attempting to define the clinical benefit of radiation in the metastatic setting for patients with limited metastases.
Mark Klein. How do you select patients for radiation in this particular situation; How do you approach stratification when radiation is started upfront?
Abhishek Solanki. In the STAMPEDE trial, low metastatic burden was defined based on the definition in the CHAARTED trial, which was those patients who did not have ≥ 4 bone metastases with ≥ 1 outside the vertebral bodies or pelvis, and did not have visceral metastases.7 That’s tough, because this definition could be a patient with a solitary bone metastasis but also could include some patients who have involved nodes extending all the way up to the retroperitoneal nodes—that is a fairly heterogeneous population. What we have done at our institution is select patients who have 3 to 5 metastases, administer prostate radiation therapy, and add stereotactic body radiation therapy (SBRT) for the other sites of disease, invoking the oligometastasis approach.
We have been doing this more frequently in the last few months. Typically, we’ll do 3 to 5 fractions of SBRT to metastases. For the primary, if the patient chooses SBRT, we’ll take that approach. If the patient chooses a more standard fractionation, we’ll do 20 treatments, but from a logistic perspective, most patients would rather come in for 5 treatments than 20. We also typically would start these patients on systemic hormonal therapy.
Mark Klein. At that point, are they referred back to medical oncology for surveillance?
Abhishek Solanki. Yes, they are followed by medical oncology and radiation oncology, and typically would continue hormonal therapy.
Mark Klein. Julie, how have you thought about presenting the therapeutic options for those patients who would be either eligible for docetaxel with high-bulk disease or abiraterone? Do you find patients prefer one or the other?
Julie Graff. I try to be very open about all the possibilities, and I present both. I don’t just decide for the patient chemotherapy vs abiraterone, but after we talk about it, most of my patients do opt for the abiraterone. I had a patient referred from the community—we are seeing more and more of this because abiraterone is so expensive—whose ejection fraction was about 38%. I said to that patient, “we could do chemotherapy, but we shouldn’t do abiraterone.” But usually it’s not that clear-cut.
Elizabeth Hansen. There was also an update from the STAMPEDE trial published recently comparing upfront abiraterone and prednisone to docetaxel (18 weeks) in advanced or metastatic prostate cancer. Results from this trial indicated a nearly identical overall survival (OS) (hazard ratio [HR] = 1.16; 95% CI, 0.82-1.65; P = .40). However, the failure-free survival (HR = 0.51; 95% CI, 0.39-0.67; P < .001) and progression-free survival (PFS) (HR= 0.65; 95% CI, 0.0.48-0.88; P = .005) favored abiraterone.8,9 The authors argue that while there was no change in OS, this trial demonstrates an important difference in the pattern of treatment failure.
