The clinical usefulness of the intraoperative detection of sentinel lymph node metastases by a rapid RT-PCR system in patients with gastric cancer

BACKGROUND The incidence of pathological lymph node metastases in patients with gastric cancer is 5% to 10%, which means that approximately 90% of patients with gastric cancer may undergo unnecessary lymphadenectomy. The precise intraoperative diagnosis of sentinel lymph node (SN) metastases is essential. The purpose of the current study was to verify the usefulness of a rapid reverse transcriptase-polymerase chain reaction (RT-PCR) system compared with hematoxylin and eosin staining for such diagnoses. METHODS A total of 113 patients with clinical T1-T2 (cT1-T2) gastric cancer, including 73 patients with cT1cN0 disease with a tumor diameter <4 cm, were enrolled in the current study. SNs were identified by a radioisotope method. Carcinoembryonic antigen and cytokeratin 19 were used as markers for RT-PCR and the cutoff values were set using 1701 lymph nodes harvested from 157 patients with gastric cancer. RESULTS SNs were detected in all 113 patients. Sensitivity and accuracy for detection by paraffin section were both 100% in patients with cT1 disease and were 60% and 90%, respectively, in patients with cT2 disease. The sensitivity of RT-PCR for the detection of pathological SN metastases was 92.3%. Furthermore, 11 patients had SN metastases detected only by RT-PCR, and these patients had frequent lymphatic invasion. Hematoxylin and eosin staining detected SN metastases in 6 of 73 patients with cT1cN0 gastric cancer; RT-PCR and frozen section detected SN metastases in 6 and 4 of these patients, respectively. Accordingly, the sensitivity of RT-PCR and frozen section for the detection of those pathological SN metastases were 100% and 66.6%, respectively. CONCLUSIONS The rapid RT-PCR system appears to have clinical usefulness for the intraoperative detection of SN metastases in patients with gastric cancer. Cancer 2016;122:386-392.