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

Abstract

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.