Background: Prostate cancer (PC) is the most commonly diagnosed noncutaneous malignancy in American men. PC, which exhibits a slow growth rate and multiple potential target epitopes, is an ideal candidate for immunotherapy. GVAX for prostate cancer is a cellular immunotherapy, composed of PC-3 cells (CG1940) and LNCaP cells (CG8711). Each of the components is a prostate adenocarcinoma cell line that has been genetically modified to secrete granulocyte-macrophage colony-stimulating factor. Hypothesizing that GVAX for prostate cancer could be effective in a neoadjuvant setting in patients with locally advanced disease, we initiated a phase II trial of neoadjuvant docetaxel and GVAX. For the trial, the clinical effects of GVAX were assessed in patients undergoing radical prostatectomy (RP).
Methods: Patients received docetaxel administered at a dose of 75 mg/m(2) every 3 weeks for 4 cycles. GVAX was administered 2-3 days after chemotherapy preoperatively for four courses of immunotherapy. The first dose of GVAX was a prime immunotherapy of 5×10(8) cells. The subsequent boost immunotherapies consisted of 3×10(8) cells. After RP, patients received an additional six courses of immunotherapy. Pathologic complete response, toxicity, and clinical response were assessed. The primary endpoint of the trial was a pathologic state of pT0, which is defined as no evidence of cancer in the prostate.
Results: Six patients completed neoadjuvant docetaxel and GVAX therapy. No serious drug-related adverse events were observed. Median change in prostate-specific antigen (PSA) following neoadjuvant therapy was 1.47 ng/ml. One patient did not undergo RP due to the discovery of positive lymph nodes during exploration. Of the five patients completing RP, four had a downstaging of their Gleason score. Undetectable PSA was achieved in three patients at 2 months after RP and in two patients at 3 years after RP.
Conclusions: Neoadjuvant docetaxel/GVAX is safe and well tolerated in patients with high-risk locally advanced PC. No evidence of increased intraoperative hemorrhage or increased length of hospital stay postoperatively was noted. These results justify further study of neoadjuvant immunotherapy.
Trial registration: ClinicalTrials.gov NCT00089856.