Addition of docetaxel, zoledronic acid, or both to first-line long-term hormone therapy in prostate cancer (STAMPEDE): survival results from an adaptive, multiarm, multistage, platform randomised controlled trial

Abstract

Background: Long-term hormone therapy has been the standard of care for advanced prostate cancer since the 1940s. STAMPEDE is a randomised controlled trial using a multiarm, multistage platform design. It recruits men with high-risk, locally advanced, metastatic or recurrent prostate cancer who are starting first-line long-term hormone therapy. We report primary survival results for three research comparisons testing the addition of zoledronic acid, docetaxel, or their combination to standard of care versus standard of care alone.

Methods: Standard of care was hormone therapy for at least 2 years; radiotherapy was encouraged for men with N0M0 disease to November, 2011, then mandated; radiotherapy was optional for men with node-positive non-metastatic (N+M0) disease. Stratified randomisation (via minimisation) allocated men 2:1:1:1 to standard of care only (SOC-only; control), standard of care plus zoledronic acid (SOC + ZA), standard of care plus docetaxel (SOC + Doc), or standard of care with both zoledronic acid and docetaxel (SOC + ZA + Doc). Zoledronic acid (4 mg) was given for six 3-weekly cycles, then 4-weekly until 2 years, and docetaxel (75 mg/m(2)) for six 3-weekly cycles with prednisolone 10 mg daily. There was no blinding to treatment allocation. The primary outcome measure was overall survival. Pairwise comparisons of research versus control had 90% power at 2·5% one-sided α for hazard ratio (HR) 0·75, requiring roughly 400 control arm deaths. Statistical analyses were undertaken with standard log-rank-type methods for time-to-event data, with hazard ratios (HRs) and 95% CIs derived from adjusted Cox models. This trial is registered at ClinicalTrials.gov (NCT00268476) and ControlledTrials.com (ISRCTN78818544).

Findings: 2962 men were randomly assigned to four groups between Oct 5, 2005, and March 31, 2013. Median age was 65 years (IQR 60-71). 1817 (61%) men had M+ disease, 448 (15%) had N+/X M0, and 697 (24%) had N0M0. 165 (6%) men were previously treated with local therapy, and median prostate-specific antigen was 65 ng/mL (IQR 23-184). Median follow-up was 43 months (IQR 30-60). There were 415 deaths in the control group (347 [84%] prostate cancer). Median overall survival was 71 months (IQR 32 to not reached) for SOC-only, not reached (32 to not reached) for SOC + ZA (HR 0·94, 95% CI 0·79-1·11; p=0·450), 81 months (41 to not reached) for SOC + Doc (0·78, 0·66-0·93; p=0·006), and 76 months (39 to not reached) for SOC + ZA + Doc (0·82, 0·69-0·97; p=0·022). There was no evidence of heterogeneity in treatment effect (for any of the treatments) across prespecified subsets. Grade 3-5 adverse events were reported for 399 (32%) patients receiving SOC, 197 (32%) receiving SOC + ZA, 288 (52%) receiving SOC + Doc, and 269 (52%) receiving SOC + ZA + Doc.

Interpretation: Zoledronic acid showed no evidence of survival improvement and should not be part of standard of care for this population. Docetaxel chemotherapy, given at the time of long-term hormone therapy initiation, showed evidence of improved survival accompanied by an increase in adverse events. Docetaxel treatment should become part of standard of care for adequately fit men commencing long-term hormone therapy.

Funding: Cancer Research UK, Medical Research Council, Novartis, Sanofi-Aventis, Pfizer, Janssen, Astellas, NIHR Clinical Research Network, Swiss Group for Clinical Cancer Research.

Figure 1

Trial profile SOC-only=standard of care only. SOC + ZA=standard of care plus zoledronic acid. SOC + Doc=standard of care plus docetaxel. SOC + ZA + Doc=standard of care plus zoledronic acid and docetaxel.

Figure 2

Failure-free and overall survival Figure shows Kaplan-Meier curves and flexible parametric models fitted to the data. Number at risk (events) shows the number of individuals at risk (ie, the number who were event free) at each timepoint, with parentheses showing the number of individuals who developed events in the period between each timepoint. SOC-only=standard of care only. SOC + ZA=standard of care plus zoledronic acid. SOC + Doc=standard of care plus docetaxel. SOC + ZA + Doc=standard of care plus zoledronic acid and docetaxel.

Figure 3

Forest plots of treatment effect on survival within subsets Data are deaths/N or HR (95% CI). All p values were statistically non-significant. For SOC-only vs SOC + ZA, all p>0·09, PSA p=0·116, time-period p=1·000. For SOC-only vs SOC + Doc, all p>0·06, PSA p=0·589, time-period p=1·000. For SOC-only vs SOC + ZA + Doc, all p>0·23 except previously treated p=0·023, PSA p=0·254, time-period p=1·000. X axis provided with natural log scaling. SOC-only=standard of care only. SOC + ZA=standard of care plus zoledronic acid. SOC + Doc=standard of care plus docetaxel. SOC + ZA + Doc=standard of care plus zoledronic acid and docetaxel. PSA=prostate-specific antigen. NSAID=non-steroidal anti-inflammatory drug.

Figure 4

Time to treatment after progression Figure shows treatments ever used at relapse, at the discretion of the treating clinician, by group, cumulative incidence curves. (A) Time to any treatment after progression. (B) Time to any life-prolonging treatment after progression. (C) Time to docetaxel after progression. (D) Time to abiraterone after progression. SOC-only=standard of care only. SOC + ZA=standard of care plus zoledronic acid. SOC + Doc=standard of care plus docetaxel. SOC + ZA + Doc=standard of care plus zoledronic acid and docetaxel. FFS=failure-free survival.