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.