Frequency of lymph node metastasis according to tumor location in clinical T1 early gastric cancer: supplementary analysis of the Japan Clinical Oncology Group study (JCOG0912)

Background The frequency of lymph node metastases per lymph node site in early gastric cancer has not been well clarified from the data based on prospective studies. This exploratory analysis aimed to determine the frequency and location of lymph node metastases in clinical T1 gastric cancer using the data from JCOG0912 to investigate the validity of the extent of standard lymph node dissection defined in Japanese guidelines. Methods This analysis included 815 patients with clinical T1 gastric cancer. The proportion of pathological metastasis was identified for each lymph node site per tumor location (middle third and lower third) and four equal parts of the gastric circumference. The secondary aim was identification of the risk factor for lymph node metastasis. Results Eighty-nine patients (10.9%) had pathologically positive lymph node metastases. Although the overall frequency of metastases was low (0.3–5.4%), metastases were widely located in each lymph node sites when primary lesion was in the middle third of the stomach. No. 4sb and 9 showed no metastasis when primary lesion was in the lower third of the stomach. Lymph node dissection of metastatic nodes resulted in a 5-year survival in more than 50% of patients. A tumor greater than 3 cm and a T1b tumor were associated with lymph node metastasis. Conclusions This supplementary analysis demonstrated that nodal metastasis from early gastric cancer is widely and disorderly not depending on the location. Thus, systematic lymph node dissection is necessary to cure the early gastric cancer.