Preferentially examined sentinel nodes for sentinel node navigation surgery in gastric cancer

The intraoperative examination of the sentinel nodes (SNs) is crucial for correctly performing SN navigation surgery (SNNS). Frozen-section diagnosis is ordinarily used; however, when several SNs are being assessed in gastric cancer, which has numerous regional lymph nodes, it is difficult to examine them all correctly within the short duration of surgery. In the present study, we aimed to determine the SNs that should be preferentially examined during SNNS in gastric cancer. A total of 824 SNs were examined in 113 patients with clinically determined T1-2 gastric cancer and no apparent lymph node metastasis. We focused on the accumulation of tracers expressed by hot nodes (HNs) using the radioisotope (RI) method and green nodes (GNs) using the dye-guided method and measured the radioactivity count of the HNs (RI count). We compared these parameters between 35 metastatic and 789 non-metastatic SNs. The percentage of metastasis-positive SNs that were radioactively 'hot' and dyed green was higher compared with that of the negative SNs (89 vs. 43%, respectively; P<0.01). The RI counts of the metastasis-positive SNs were higher compared with those of the negative SNs [median (range): 361 (0-10,670) vs. 53 (0-9,931), respectively; P<0.01]. The area under the receiver operating characteristic curve of the RI count was 0.69 (95% CI: 0.60-0.78). Therefore, when assessing several SNs, those with higher RI counts (HNs and GNs) should be preferentially examined. Further accumulation of cases is required to establish the cut-off value for the diagnosis of metastasis based on the RI count.