This suggests that lymph nodes (LNs) contain micro-metastases that are not identified by the pathologist. In this study, they evaluated different markers such as PSA, EpCAM, AR, PSCA, a2 integrin, a6 integrin, periostin, CD11b and CD68 in LNs of patients undergoing radical prostatectomy with extended PLND by quantitative RT-PCR. These results were then correlated with histopathology. In initially establishing the methodology, differential marker expression of lymph nodes of both men and women undergoing different surgical interventions for benign and malignant disease were analyzed by RT-PCR. After marker evaluation, retained markers were evaluated in 13 men undergoing radical prostatectomy with extended PLND and compared to histopathology. LNs were split lengthwise; half of the lymph LN was evaluated by histopathology and the other half underwent RNA extraction and quantitative RT-PCR.
Median number of LNs removed was 31. Among the markers evaluated, PSA, EpCAM, and PSCA were retained for further evaluation, as the other markers were also positive in the control tissues. Pathologically confirmed positive LNs in 3 patients expressed PSA, AR, EpCAM and PSCA. In 2 of these 3 patients, 7 pathologically negative LNs were RT-PCR positive. In 5/10 (50%) of pN0 patients quantitative RT-PCR was positive for 1 or 2 markers without histological evidence of tumor. It will be interesting to see if these patients ultimately recur. This type of study will not be possible in archival tissue by this methodology, as RNA must be extracted from fresh or fresh-frozen tissue.
Presented by George N. Thalmann, MD, et al. at the 26th Annual European Association of Urology (EAU) Congress - March 18 - 21, 2011 - Austria Centre Vienna, Vienna, Austria