Mark Klein, MD
The STAMPEDE platform included a multiple arm and multiple stage protocol to evaluate abiraterone and enzalutamide in high risk non-metastatic and metastatic disease in separate trials. In the accompanying article by Attard et. al, a meta-analysis of two separate trials conducted as part of the STAMPEDE platform was undertaken. In the first trial, patients with high-risk localized prostate cancer were randomized to androgen deprivation therapy (ADT) with or without abiraterone. In the second trial, similar patients were randomized to ADT versus ADT plus abiraterone plus enzalutamide. The primary outcome of metastasis-free survival and secondary outcome of overall survival [OS] were significantly longer for the treatment arms over ADT; however, the addition of enzalutamide to abiraterone did not result in additional benefit. In appropriately selected patients with high risk localized prostate cancer, abiraterone is a reasonable option to consider in appropriately selected patients.
While bone is the most frequent site of metastasis in men with prostate cancer, visceral metastases (predominantly liver or lung) has been associated with worse outcomes. However, lower incidence of visceral metastases makes conduct of studies focused on visceral disease challenging. Baciarello et al conducted a post-hoc analysis of the LATITUDE study (where men with metastatic castrate-sensitive disease were treated with ADT plus abiraterone or ADT alone) in participants with visceral disease. Overall, patients with visceral metastases derived OS benefit (55.4 versus 33 months). Patients with lung metastases had similar OS to the entire cohort; however, those with liver metastases still derived benefit but had lower OS (36.8 versus 25.6 months). These post-hoc findings suggest that liver metastases present unique challenges compare to other metastatic disease sites, but further study is needed.
In the ENZAMET trial, enzalutamide plus ADT was compared to ADT alone in patients with metastatic castrate-sensitive disease, and enzalutamide treatment was associated with improved OS. In the report by Stockler et al , quality of life metrics as assessed by periodic evaluation utilizing standard questionnaires were reported. Patients who received enzalutamide reported more fatigue and lower cognitive and physical function than those receiving placebo. However, the overall quality of life did not decrease. These important quality of life findings, which are increasingly being reported in similar studies, support the overall net benefit of utilization of enzalutamide in patients with metastatic castrate-sensitive disease.