Background
Abiraterone acetate plus prednisolone previously showed a clear survival advantage in men starting long-term hormone therapy for prostate cancer in STAMPEDE, a randomized controlled trial using a multi-arm multi-stage platform design. STAMPEDE included a wide range of men with M1 or M0 disease. The LATITUDE trial, in patients with high-burden M1 disease only, reported a similar magnitude of effect to the comparable subset of STAMPEDE pts. We report long-term outcomes in the M1 subset of pts in STAMPEDE.
Methods
All patients received androgen deprivation therapy (ADT). Stratified randomization allocated pts 1:1 to ADT alone or adding daily abiraterone acetate 1000mg + prednisolone 5mg (SOC+AAP) continued until PSA, radiological & clinical progression. The primary outcome measure was death from any cause. The data freeze for this long-term analysis was planned for 3yr after the primary survival results when a meaningful increase in data was anticipated. Analyses used Cox proportional hazards & flexible parametric models, adjusted for baseline stratification factors.
Results
Of 1,917 pts contemporaneously randomized to these groups (Nov-2011 to Jan-2014), 1,003 (52%) had M1 disease. The M1 groups were balanced: median age 67yr; 48% high-burden, 44% low-burden, 8% burden not assessable; 94% newly-diagnosed; median PSA 97ng/ml. Median follow-up had increased from 3.5yr to 6.1yr & number of ADT-only deaths increased by 50%, from 218 previously to 329. With 244 ADT+AAP deaths, the adjusted HR=0·60 (95%CI 0·50—0·71; p=0.31×10-9) favouring ADT+AAP, with 5-yr survival improved from 41% ADT-only to 60% ADT+AAP. The relative effect of abiraterone was similar in low-burden (HR=0·55; 95%CI 0·41—0·76) and high-burden (HR=0·54; 95%CI 0·43—0·69) patients. Median time on ADT+AAP was 2.4yr, with a current maximum of 8.1yr. Toxicity at 4yr post-randomisation was similar, with 16% of patients in each group reporting grade 3 or higher toxicity.
Conclusions
A sustained and substantial improvement in overall survival of M1 prostate cancer patients was achieved with ADT + abiraterone acetate + prednisolone, irrespective of burden of disease.