The STAMPEDE Trial Long Term Follow-Up Data

Transcript: Alicia Morgans, MD, MPH: STAMPEDE is an outstanding effort by our colleagues in the UK [United Kingdom] to perform a really important study in patients who have metastatic castration-sensitive prostate cancer, or mCSPC. This multiarm trial includes a control arm that’s been enrolling continually for years now. Over time, new arms with new therapies are added as the therapeutic experimental arm along the way. The most recent data that we heard at ESMO [the European Society for Medical Oncology Congress] looks at this metastatic CSPC population, which is actually a bit of a hodgepodge of predominantly de novo metastatic disease patients. Some patients with nonmetastatic high-risk disease have an elevated PSA [prostate-specific antigen] but no evidence of metastases.

In this latest data, we looked at this metastatic CSPC population, and the investigators went back in the docetaxel-treated arm and looked at that arm by high- and low-volume disease status. We remember that high- and low-volume disease was defined in the CHAARTED trial, with high-volume disease being at least 4 bone metastases with at least 1 outside the axial skeleton, or visceral metastases. And in CHAARTED, importantly, we saw that there was a benefit to docetaxel plus ADT [androgen deprivation therapy] versus ADT alone in the high-volume patient population but not in the low-volume patient population.

In the STAMPEDE study, they looked at this population by these definitions and found that the benefit of chemotherapy—hormonal therapy, or docetaxel plus ADT, actually spanned both the high-volume and low-volume patient populations. This was in stark contrast to CHAARTED, which was really exciting but a little mind-blowing. What we heard discussed, though, was that STAMPEDE was predominantly de novo metastatic disease, so most of these patients came into the trial not having had treatment for their primary prostate cancer. In that population, there seemed to be a universal benefit.

In CHAARTED, actually, particularly in the low-volume disease population, these patients had treatment of the primary prostate cancer first, and this was recurrent disease. And so the explanation by the authors—and this was repeated and agreed upon by most people in the audience—is that because the case mix of de novo metastatic versus being recurrent after treatment of the primary is probably what drove this difference. In any event, in de novo metastatic disease, what STAMPEDE tells us is that chemotherapy—hormonal therapy looks as though it’s beneficial, whether patients had high- or low-volume disease.

The new finding from STAMPEDE—finding that high- and low-volume patients both seem to benefit from chemotherapy—hormonal therapy in metastatic CSPC—gives the opportunity for clinicians to give another option to patients for treatment. Previously, at least in the United States, we were really relying on the CHAARTED data to understand that high-volume disease seemed to benefit from chemotherapy–hormonal therapy, but that low-volume patients may not benefit in the same way. And so we were limited in our options for treating those patients. In the UK, actually, they were treating patients across the spectrum but didn’t necessarily know if they were benefiting those patients with low-volume disease. We now know that [chemotherapy]–hormonal therapy appears to benefit everyone as long as their disease is de novo metastatic. And so it gives us an opportunity to prolong survival and hopefully improve the quality of life for more patients.

Transcript Edited for Clarity