Also reported at the meeting were several analyses of the Phase III AFFIRM trial of men with castration-resistant prostate cancer receiving enzalutamide after treatment with docetaxel.
Mark T. Fleming, MD, of Virginia Oncology Associates, reported a study about the long-term responders to enzalutamide in that study (Abstract 20). Patients were randomized to receive either enzalutamide at 160 mg/day or placebo. Patients in the enzalutamide group were allowed to continue on that drug even after the study was unblinded.
A total of 35 percent (276 of 800 patients) of the enzalutamide group were on therapy for at least 12 months, and 22 percent (174 patients) were on therapy for more than 18 months.
Fleming said that comparing the subgroup of long-term responders with the “all-enzalutamide” group, the long-term responders had been living with prostate cancer longer (7.9 vs. 5.9 years) and had a lower disease burden at baseline.
The long-term responding patients had improved efficacy outcomes compared with the all-enzalutamide group. Of note, he said, the 50 percent PSA response was 87 percent in the long-term responders vs. 54 percent in the all-enzalutamide group.
In another study related to the AFFIRM data, Howard Scher, MD, Chief of the Genitourinary Oncology Service and the D. Wayne Calloway Chair in Urologic Oncology at Memorial Sloan-Kettering Cancer Center, also a coauthor of the long-term responders study, reported that use of corticosteroids in patients with metastatic castration-resistant prostate cancer during treatment with docetaxel resulted in reduced overall survival and more grade 3/4 toxicity, as had been previously been shown for use at baseline before the study started (Abstract 6).
Still, he noted, while patients taking corticosteroids had worse outcomes, the results in patients treated with enzalutamide were consistently superior to the placebo group regardless of whether they used or did not use corticosteroids. “The inferior outcomes in corticosteroid patients may be due to unmeasured confounders or the biologic properties of corticosteroid use itself,” he said.
In another analysis of the AFFIRM data, Cora Sternberg, MD, Chief of Medical Oncology at San-Camillo Forlanini Hospital in Rome, found that treatment with enzalutamide significantly improved outcomes in both older and younger patients (i.e., those 75 and older, and younger than 75), and the safety and tolerability results were also comparable (Abstract 16).