Epithelial tumour cell detection and the unsolved problems of nested RT-PCR: A new sensitive one step method without false positive results

Sensitive detection of circulating epithelial cancer cells might have important therapeutic and prognostic implications in patients with breast cancer (BC) receiving high-dose chemotherapy and PBSC support. We have compared the specificity and sensitivity of the recently developed 'one tube' reverse transcriptase PCR (RT-PCR) assay with the more widely used nested RT-PCR method for detection of cytokeratin 19 (CK19)-positive cells. The analysis of 30 control samples provides evidence that one tube RT-PCR is highly specific in contrast to the nested method which showed 23% false positive results. The sensitivity of both techniques to detect tumour contamination was 10(-6). PBSC harvests from 45 BC patients were tested with both RT-PCR methods and the results were compared with immunocytochemistry (ICC), The five samples found positive by ICC were also positive by one tube RT-PCR; in addition, 11 more samples were positive by one tube RT-PCR analysis. The greater number of PBSC found positive by one tube RT-PCR might be due to the larger number of cells analysed. We conclude that one tube RT-PCR is sensitive and reveals no false positive results. This method is less time consuming than the nested one, technically simpler and should be considered for tumour cell detection.