The use of trastuzumab in the treatment of hormone refractory prostate cancer; phase II trial

PURPOSE. To investigate the efficacy and toxicity of the antibody to the HER-2/neu receptor (trastuzumab, Herceptin®) in the treatment of advanced hormone-refractory prostate cancer (HRPC). MATERIALS AND METHODS. Eighteen patients with HRPC were recruited for this phase II trial in which they received trastuzumab for 12 weeks or until disease progression or unacceptable toxicity was documented. HER-2 receptor overexpression was evaluated using immunohistochemistry (IHC) and dual-color fluorescence in-situ hybridization (FISH) assays. RESULTS. Trastuzumab as a single agent demonstrated little efficacy in treating HRPC. Two patients demonstrated stable disease based on a decrease in PSA level to less than 50% of baseline. No patient demonstrated a regression of radiographic bony or soft tissue metastatic disease. The medication was well tolerated in 16 patients (89%), and 2 patients (11%) had to be hospitalized for cardiac complications. CONCLUSIONS. Trastuzumab (Herceptin®) as a single agent demonstrated poor efficacy in treating HRPC. Based on promising results in treating breast cancer with regimens using Herceptin® and cytotoxic agents, a similar combination approach might demonstrate better efficacy in treating HRPC.