Prostate specific antigen negative prostate cancer

• Main Author: Birtle, A. J.
• Published: University College London (University of London) 2005
• Subjects: 616.99
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.634555

Prostate specific antigen (PSA) has been used in the diagnosis and monitoring of prostate cancer for almost 20 years. Most men who present with metastatic prostate cancer have markedly elevated serum levels of PSA. However, approximately 1% of cases have serum PSA levels that are much lower than the tumour burden would suggest - so-called "PSA-Negative" tumours. Their diagnosis may be delayed, and management compromised. Little is known about this patient group. The aim of this study was to improve the understanding and management of "PSA-negative" prostate cancer. The clinical history and tissue from 33 patients who presented with treatment-naive metastatic prostate cancer and a serum PSA < 10 ng/ml were included in this study, the largest series so far reported. Clinical and immunohistochemical features were defined and alternative biomarkers investigated. Potential mechanisms underlying PSA-negativity were explored using prostate cancer cell lines and archival tissue. From the clinical case notes review, patients presenting with low serum PSA and metastatic prostate cancer have a similar pattern of disease to men with high PSA prostate cancer. However, response duration to first line hormonal treatment and overall survival were shorter. Immunohistochemistry performed on archival prostatic tissue has shown that the majority of the cancers are positive for PSA, despite low serum levels. The extent of PSA immunostaining is patchy and could be missed on biopsy. PSMA and AR are expressed, however, and represent alternative diagnostic aids. The study indicates that PSMA and PAP should be explored as potential serum biomarkers in this patient group. The androgen receptor (AR) remains expressed in over 90 % of these cases and therefore defects in this pathway are unlikely to explain the low serum PSA levels. Neither loss of heterozygosity nor gene methylation of AR or PSA appear to be mechanisms underlying low serum PSA levels.