Improved sensitivity for detecting micrometastases in pelvic lymph nodes by real-time reverse transcriptase polymerase chain reaction (RT-PCR) compared with conventional RT-PCR in patients with clinically localized prostate cancer undergoing radical prostatectomy.

OBJECTIVE

To compare the usefulness between real-time reverse transcriptase polymerase chain reaction (RT-PCR) with that of conventional RT-PCR for detecting micrometastases in pelvic lymph nodes (PLN) dissected during radical prostatectomy (RP) for prostate cancer.

PATIENTS AND METHODS

In all, 120 patients with clinically localized prostate cancer who underwent RP and pelvic lymphadenectomy were included. Expression of prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) in 2215 PLNs obtained from these 120 patients were assessed by fully quantitative real-time RT-PCR and as well as conventional RT-PCR. Specimens, in which either PSA or PSMA mRNA was positive, were regarded as showing the 'presence of micrometastasis'.

RESULTS

Pathological examinations detected tumour cells in 29 PLNs from 11 patients, while real-time RT-PCR and conventional RT-PCR further identified micrometastasis in 143 and 81 PLNs from 32 and 19 patients, respectively, with no pathological evidence of nodal involvement; that is, the sensitivity of real-time RT-PCR for detecting micrometastases was significantly higher than that of conventional RT-PCR. In this series, biochemical recurrence occurred in 32 patients, and in both assays, there were significant differences in biochemical recurrence-free survival between patients with and with no micrometastases. However, despite the significant association of micrometastases detected by both assays with biochemical recurrence on univariate analysis, the presence of micrometastases detected by real-time RT-PCR but not that detected by conventional RT-PCR appeared to be useful as an independent predictor on multivariate analysis.

CONCLUSION

Although micrometastatic tumour foci in PLNs that were missed by routine pathological examination could be diagnosed by both real-time RT-PCR and conventional RT-PCR assays, it would be strongly recommended to use real-time RT-PCR to detect micrometastases considering its high sensitivity and the close association between the outcome of this assay and the probability of biochemical recurrence.