Lapatinib in Treating Patients With Recurrent or Metastatic Prostate Cancer

PRIMARY OBJECTIVES: I. To determine the antitumor activity of GW572016 in hormone naïve, recurrent and/or metastatic hormone sensitive prostate cancer using PSA response rate. SECONDARY OBJECTIVES: I. To estimate objective tumor response in patients with measurable disease. II. To determine the duration of PSA response, rate and duration of stable disease, progression-free, median and overall survival rates of GW572016 in recurrent and/or metastatic prostate cancer. III. To document the safety and tolerability of GW572016 in these patient populations. TERTIARY OBJECTIVES: I. To investigate if differences in baseline levels of EGFR and/or erbB2 expression, and receptor phosphorylation status in tumor specimens predict outcome to therapy. II. To investigate if the inhibitory effects of GW572016 on EGFR and/or erbB2 pathway activation in tumor specimens correlates with clinical outcome. OUTLINE: This is a nonrandomized, open-label, multicenter study. Patients receive oral lapatinib once daily on days 1-28. Courses repeat every 28 days in the absence of unacceptable toxicity or disease progression. Patients are followed for survival. PROJECTED ACCRUAL: A total of 21-41 patients will be accrued for this study within 11.7 months.