A national multicenter phase 2 study of prostate-specific antigen (PSA) pox virus vaccine with sequential androgen ablation therapy in patients with PSA progression: ECOG 980 - Abstract

BACKGROUND: E9802 was a phase 2 multi-institution study conducted to evaluate the safety and effectiveness of vaccinia and fowlpox prostate-specific antigen (PSA) vaccine (step 1) followed by combination with androgen ablation therapy (step 2) in patients with PSA progression without visible metastasis.

OBJECTIVE: To test the hypothesis that vaccine therapy in this early disease setting will be safe and have a biochemical effect that would support future studies of immunotherapy in patients with minimal disease burden.

DESIGN, SETTING, AND PARTICIPANTS: Patients who had PSA progression following local therapy were treated with PROSTVAC-V (vaccinia)/TRICOM on cycle 1 followed by PROSTVAC-F (fowlpox)/TRICOM for subsequent cycles in combination with granulocyte-macrophage colony-stimulating factor (step 1). Androgen ablation was added on progression (step 2).

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Step 1 primary end points included progression at 6 mo and characterization of change in PSA velocity pretreatment to post-treatment. Step 2 end points included PSA response with combined vaccine and androgen ablation.

RESULTS AND LIMITATIONS: In step 1, 25 of 40 eligible patients (63%) were progression free at 6 mo after registration (90% confidence interval [CI], 48-75). The median pretreatment PSA velocity was 0.13 log(PSA)/mo, in contrast to median postregistration velocity of 0.09 log(PSA)/mo (p=0.02), which is an increase in median PSA doubling time from 5.3 mo to 7.7 mo. No grade ≥4 treatment-related toxicity was observed. In the 27 patients eligible and treated for step 2, 20 patients achieved a complete response (CR) at 7 mo (CR rate: 74%; 90% CI, 57-87). Although supportive of larger studies in the cooperative group setting, this study is limited by the small number of patients and the absence of a control group as in a phase 3 study.

CONCLUSIONS: A viral PSA vaccine can be administered safely in the multi-institutional cooperative group setting to patients with minimal disease volume alone and combined with androgen ablation, supporting the feasibility of future phase 3 studies in this population.

PATIENT SUMMARY: These data support consideration of vaccine therapy earlier in the course of prostate cancer progression with minimal disease burden in future studies of vaccine approaches in earlier stages of disease.

Written by:
DiPaola RS, Chen YH, Bubley GJ, Stein MN, Hahn NM, Carducci MA, Lattime EC, Gulley JL, Arlen PM, Butterfield LH, Wilding G.   Are you the author?
Rutgers Cancer Institute of New Jersey, New Brunswick, NJ, USA; Dana-Farber Cancer Institute, Boston, MA, USA; Beth Israel Deaconess Medical Center, Boston, MA, USA; Indiana University Simon Cancer Center, Indianapolis, IN, USA; Johns Hopkins University, Baltimore, MD, USA; National Cancer Institute, Bethesda, MD, USA; University of Pittsburgh, Pittsburgh, PA, USA; UW Carbone Cancer Center, University of Wisconsin, Madison, WI, USA.  

Reference: Eur Urol. 2014 Dec 18. pii: S0302-2838(14)01265-2.
doi: 10.1016/j.eururo.2014.12.010

PubMed Abstract
PMID: 25533418

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