Impact of baseline disease volume and prior docetaxel therapy on PSA-related outcomes in patients with mHSPC receiving enzalu-tamide plus ADT.

Background: Enzalutamide plus androgen deprivation therapy (ADT) significantly reduced the risk of radiographic progression or death in men with metastatic hormone-sensitive prostate cancer (mHSPC), regardless of baseline prostate-specific antigen (PSA) levels (ARCHES; NCT02677896). Here, we further assess PSA-related outcomes in pa-tients enrolled in ARCHES by disease volume and prior docetaxel ther-apy at study entry. Method(s): Patients with mHSPC (n=1150) were randomised 1:1 to en-zalutamide (160 mg/day) plus ADT or placebo plus ADT. Primary end-point was radiographic progression-free survival. Secondary endpoints included time to PSA progression and PSA undetectable rate. Post hoc analyses were based on disease volume and prior docetaxel at study entry, which were stratification factors, as well as time to 50% PSA re-duction and time to undetectable (< 0.2 ng/mL) PSA. Result(s): Overall, 423 (36.8%) patients had low-volume disease and 205 (17.8%) patients reported prior docetaxel use. Enzalutamide plus ADT significantly improved PSA-related outcomes versus placebo plus ADT, regardless of disease volume or prior docetaxel use at study entry (Ta-ble). The proportion of patients with >=50% PSA reduction from baseline was 85-95% for enzalutamide plus ADT and 18-66% for placebo plus ADT across subgroups. Conclusion(s): Enzalutamide plus ADT improved all assessed PSA-related outcomes versus placebo plus ADT in patients with mHSPC, ir-respective of disease volume or prior docetaxel therapy. True baseline PSA is unknown for some patients due to prior ADT use in this popula-tion. (Figure Presented).