Intraoperative sentinel lymph node mapping in stage I non-small cell lung cancer: detection of micrometastases by polymerase chain reaction.

OBJECTIVE We previously reported the results achieved in detecting sentinel lymph nodes (SLN). We applied the molecular techniques (RT-PCR) to improve the detection of micrometastasis in order to evaluate an improvement of staging in early non-small cell lung cancer (NSCLC) patients (pts). METHODS This study was carried out on 22 consecutive NSCLC pts with stage I disease. A dose of 37MBq (1 ml (99m)Tc-nanocolloid suspension) was administered. The intralesional injection was performed under CT-guidance (7 pts), by using bronchoscopy (5 pts), VATS (2 pts) and at time of the thoracotomy (8 pts). RT-PCR analysis for cytokeratin 7 and 19 (CK7-CK19) was used to identify tumour-derived material in lymph nodes (LN). Each SLN was bisected: half was used for conventional examination (H&E staining/by immunohistochemistry (IHC), half was snap-frozen to -80 degrees C for RNA-detection of CK7 and CK19. RESULTS SLN was detected in 16 out of 19 pts. In three pts SLN was not identified (due to an incorrect technique). Conventional pathologic examination showed stage I disease in 13 pts, T3N0 disease in 1 pt, N2 in 5 pts. The IHC analysis identified micrometastasis in seven pts (two evaluated N0 according to H&E staining). RT-PCR analysis, performed in 10/16 pts, identified micrometastasis in 6 pts (3 pts evaluated N0 disease by H&E ; 1 of these evaluated N0 even by IHC). All N2 patients relapsed. One patient (N0 pts after H&E and IHC analysis) with positive CK7 and CK19 expression by RT-PCR analysis relapsed (systemic relapse) 3 months after surgery. CONCLUSIONS SLN technique could provide a subgroup of patients in which the use of RT-PCR could be applied on a well-focused target. This approach may be useful for stratifying histologically N0 patients into higher risk and lower risk groups.