The molecular staging of prostate cancer.

The natural history of prostate cancer is notoriously variable and whilst some tumours remain indolent for many years, others result in rapid progression to metastasis and death. A substantial minority of patients treated with radical prostatectomy or radiotherapy with curative intent have rising levels of PSA in their serum after treatment, and this is often associated with the eventual development of metastases. It is possible that some of these patients already have ‘micrometastases’ at the time of treatment. No staging investigation is able to predict reliably which patients will be cured by radical treatment. Radionuclide bone scans are positive in only 5% of patients with a serum PSA of <20 ng/mL [1], although a substantial number of patients with negative bone scans will not be cured. CT and MRI are not reliable for local staging of tumours and newer investigations, e.g. positron emission tomography and immunoscintigraphy, are as yet unable to detect micrometastases. Partin’s tables, which use serum PSA, clinical stage and Gleason grade to predict local stage and the likelihood of lymph node involvement, are commonly used to assess the chances of a localized prostatic tumour being cured by radical surgery [2]. These tables depend on the accuracy of clinical staging by a DRE and the histological grade of biopsy material, neither of which is entirely dependable.