Reverse transcriptase- polymerase chain reaction (RT-PCR) to detect prostate cancer micrometastasis in the blood.

Abstract

Since the high mortality rate of prostate cancer is directly associated with the incidence of cancer metastasis, early detection of metastasizing prostate cancer cells in the blood has very important clinical implications. Conventional screening and staging modalities often fail to identify patients who may have prostate cancer that is already metastatic [1], and it has been estimated that 60% of new patients may have asymptomatic micrometastasis. It is therefore of great importance to be able to define which patients are at risk for the development of further metastatic disease [2,3]. It has been suggested that the detection of circulating prostate cancer cells in the peripheral blood may allow assessment of disease state [4], although the exact clinical significance of circulating cancer cells remains unclear. Animal experiments using solid tumors have shown that only two cells per milliliter of blood may be enough for tumor metastasis from hematogenous dissemination [5–7]. Based on these studies, a technique to detect circulating cells must be highly sensitive, detecting ten tumor cells in a five milliliter blood sample. Although immunohistochemical and other immunological techniques that use antibodies against tumor-associated antigens or tissue-specific antigens are helpful in detecting the primary site of metastatic disease and the presence of small foci of metastatic disease, these techniques are not sensitive enough to detect such a small number of cancer cells in a large quantity of nonneoplastic cells. It is through the development of Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) and new tumor markers that the desired sensitivity for this approach becomes possible. The high sensitivity and specificity obtained from this technique as well as the small quantity of test material required makes RT-PCR a definite front runner in the race for early detection of micrometastasis in prostate cancer.