How can sentinel navigation surgery abbreviate mediastinal lymph node dissection for lung cancer?

Sentinel nodes (SNs) were examined for 101 patients who had peripheral type non-small cell lung cancer less than 5 cm and had undergone systemic mediastinal lymph node dissection. The surgical procedure was lobectomy in 91, pneumonectomy in 3, and segmentectomy with lymph node dissection in 7. In the CT room, the site for RI injection was marked on the skin, and the angle and depth of the needle required to reach the peritumoral region was determined. The RI was then injected in the RI room. The radioactivity in the lymph nodes was counted before dissection (in vivo counting), and after dissection that (ex vivo counting). SNs were defined as any node for which the count was ≥10 times than the background count. SN identification was finally based on ex vivo data. Of the 101 patients, SNs could be identified in 80 patients (80%). Patients whose SNs could not be identified had a significantly lower forced expiratory volume in one second/forced vital capacity (FEV1/FVC) than those with identifiable SNs (p=0.025). Twenty six patients (33%) had SN in the mediastinum, the distribution of which depended on the lobe, ie the No.4 lymph node station in the right upper lobe, the No.4 in the right middle lobe, the No.4 and 7 in the right lower lobe, the No.5 in the left upper lobe, and the No.7 in the left lower lobe. One false negative SN was detected in 25 patients with N 1 or N 2 disease (4%). In vivo and ex vivo counting showed 73% concurrence for the identification of SNs in mediastinal lymph node stations, of which rate was significantly higher than 40% in hilar lymph node stations (p<0.001). The SNs were identifiable in 80% of lung cancer patients, with 4% false negative by using a Tc-99 m tin-colloid. SNs were difficult to identify in patients with a low level of FEV1/FVC, such as those with chronic obstructive pulmonary disease. The in vivo identification of mediastinal SNs was reliable as much as the ex vivo. Therefore, the in vivo identification of SNs in the mediastinum could be useful approach to guide mediastinal lymph node sampling or dissection. (author)