939P - Neoadjuvant sipuleucel-T in localized prostate cancer: effects on immune cells within the prostate tumor microenvironment

Date 29 September 2012
Event ESMO Congress 2012
Session Poster presentation I
Topics Prostate Cancer
Cancer Immunology and Immunotherapy
Presenter Lawrence Fong
Authors L. Fong1, V. Weinberg2, S.E. Chan2, J. Corman3, C. Amling4, R.A. Stephenson5, J. Simko2, R. Sims6, P. Carroll2, E.J. Small2
  • 1University of California, San Francisco, 94143 - San Francisco/US
  • 2Comprehensive Cancer Center, University of California, San Francisco, 94143 - San Francisco/US
  • 3Surgery, Virginia Mason Medical Center, 98111 - Seattle/US
  • 4Urology, Oregon Health & Science University, Portland/US
  • 5Urology, University of Utah, Salt Lake City/US
  • 6Clinical Affairs, Dendreon Corporation, Seattle/US

Abstract

Background

Sipuleucel-T is an FDA-approved autologous cellular immunotherapy for patients with asymptomatic or minimally symptomatic metastatic castrate resistant prostate cancer (mCRPC). To date, studies of sipuleucel-T in patients with mCRPC have studied immune response in peripheral blood. The immune effects of sipuleucel-T in prostatic cancer tissue are unknown.

Methods

NeoACT (P07-1; NCT00715104) is an open-label, Phase 2 study of patients with localized prostate cancer who received sipuleucel-T prior to radical prostatectomy (RP) to examine the immunologic effects of treatment on prostate tissue. Patients received 3 infusions of sipuleucel-T at approximately 2-week intervals, beginning 6-7 weeks prior to RP, and post-RP are being followed for immune response. The primary endpoint was the change in the frequency of lymphocytes between prostate biopsies (pre-treatment) and RP tissue (post-treatment), as assessed by immunohistochemistry (IHC).

Results

Of the 42 enrolled patients (median age 61 years, all ECOG = 0, Gleason Sum: ≤6 = 24%, 7 = 43%, ≥8 = 33%), 38 received all 3 pre-RP sipuleucel-T infusions and were evaluable by IHC. Treatment-related AEs were manageable and transient. Sipuleucel-T did not appear to affect operative complications, procedure time, or estimated blood loss. Frequent events (>10% of patients) that occurred ≤1 day after infusion were fatigue, headache, and myalgia. Significant increases (>3 fold) in infiltrating CD3 + , CD3 + /CD4 + , and CD3 + /CD8+ T cell populations were observed at the tumor rim (where benign and malignant glands interface), compared with the pretreatment biopsy (all p = 0.0001). CD3 + /CD4 + /FoxP3+ cells were also increased at the tumor rim (∼2-fold; P = 0.005), but represented a small proportion of the observed T cells. This level of T cell infiltration was not seen in a cohort of 12 concurrent cases that did not receive neoadjuvant treatment.

Conclusions

Neoadjuvant sipuleucel-T treatment is associated with an increased frequency of T cells in the prostate at the interface of the benign and malignant glands. These data demonstrate that sipuleucel-T can modulate the presence of lymphocytes at prostate cancer tissue in vivo.

Disclosure

L. Fong: Research funding from Dendreon.

R.B. Sims: Employee and stockholder of Dendreon.

P. Carroll: Honoraria from Takeda. Research funding from Myriad and Abbot,

E.J. Small: Honoraria from Dendreon.

All other authors have declared no conflicts of interest.