['This study was designed to test whether early castration-induced short-term cellular changes in primary prostate tumours could predict clinical outcome in advanced disease.', 'Biopsies from 83 patients obtained before and within two weeks after surgical castration were investigated. Tumour epithelial cell apoptosis, proliferation, and prostate specific antigen (PSA) levels were quantified using immunohistochemistry, laser capture micro-dissection, and real time RT-PCR. Cellular effects were related to changes in serum PSA levels and clinical outcome.', 'Decreased proliferation and PSA mRNA levels, and increased apoptosis were observed in most tumours. These early cellular responses were not correlated to each other and did not predict serum PSA response or cancer-specific survival. A nadir PSA level below 1 ng/ml predicted a longer cancer-specific survival after castration therapy.'] Does the magnitude of early castration-induced primary tumour regression in prostate cancer predict clinical outcome?