Intra-operative sentinel lymph node identification using a novel receptor-binding agent (technetium-99m neomannosyl human serum albumin, 99mTc-MSA) in stage I non-small cell lung cancer

Objective: In the previous report, to simplify the synthesis and labelling procedures and to improve the biological properties, we developed a novel mannose receptor-binding agent, technetium-99m human serum albumin (99mTc-MSA), for sentinel lymph node detection. This study is the first clinical trial designed to test the reliability and feasibility of sentinel node detection using this new radioactive agent in patients with stage I non-small cell lung cancer. Methods: Forty-two patients (30 men, 12 women; mean age 63.3 ± 8.9 years) that were candidates for lobectomy with mediastinal lymph node dissection for stage I non-small cell lung cancer were enrolled. A total dose of 1 mCi of 99mTc-MSA in 0.2 ml was administered in one shot at the peritumoural region approximately 3 h before surgery. The radioactivity in the lymph nodes was counted before (in vivo) and after (ex vivo) dissection with a hand-held gamma probe. A sentinel lymph node was defined as any node for which the radioactivity count was 5 times that of the resected lung tissue with the lowest count for the ex vivo counts. All harvested lymph nodes were cut into 2-mm slices and ultimately diagnosed by using formalin-fixed and paraffin-embedded sections with haematoxylin and eosin staining. Results: 99mTc-MSA was taken up by the lymph nodes and its detection did not change until 21 h after the injection. The number of dissected lymph nodes per patient was 22.1 ± 11.6 (range 4-57). Among 42 patients, the sentinel lymph nodes could be identified in 40 patients (95.2%). The number of sentinel lymph nodes identified was 2.3 ± 1.1 stations (range 1-5) per patient. Ten out of 40 patients (25.0%) had metastases in 11 sentinel lymph nodes. Three of these 11 sentinel lymph nodes (27.3%) had skip metastases. No false-negative sentinel lymph nodes were detected in any of the 10 patients with N1 or N2 disease (0%). The relationship between in vivo and ex vivo results for mediastinal sentinel lymph nodes showed concurrence in 29 out of 40 patients (72.5%). Conclusions: Intra-operative sentinel lymph node identification using 99mTc-MSA appears to be feasible and reliable in stage I non-small cell lung cancer.