Sentinel node mapping for post-endoscopic resection gastric cancer: multicenter retrospective cohort study in Japan

Background Standard gastrectomy with systematic lymphadenectomy as an additional surgery after endoscopic resection (ER) causes a deterioration in long-term quality of life. If the sentinel lymph node (SN) basin concept can be applied in post-ER gastric cancer, minimal surgery can be applied without reducing the curability. This retrospective multicenter cohort study aimed to verify the validity of the SN basin concept in post-ER gastric cancer. Patients and methods Individual data of 132 patients who underwent SN mapping after ER were collected from 8 university hospitals in Japan from 2001 to 2016. Tracers were injected endoscopically in the submucosal layer at four sites around the post-ER scar. We compared the SN basin distribution of post-ER gastric cancer with that of 275 patients with non-ER gastric cancer. Results Two cases of SN were unidentified, both involving a single tracer (SN detection rate: 98.5%). Nine cases (6.8%) of lymph node metastasis were found, of which eight had a metastatic lymph node within the SNs and one had a non-SN metastasis within the SN basin. The diagnostic sensitivity of SN mapping for lymph node metastasis was 88.9% in post-ER group and 95.7% in non-ER group (P = 0.490); the accuracy was 99.2% and 99.6% (P = 0.539), respectively. Regarding the SN basin, no significant intergroup differences were found regardless of the primary tumor location. Conclusions Our findings clarified the feasibility of SN mapping based on the SN basin concept in patients with gastric cancer who previously underwent ER.