Clinicopathologic implication of meticulous pathologic examination of regional lymph nodes in gastric cancer patients

BACKGROUND We aimed to investigate effect of increased number of examined lymph nodes (LNs) to pN category, and compare various N categories in gastric cancer: American Joint Committee on Cancer (AJCC) 7th edition, metastatic LN ratio (MLR), and log odds of positive LNs (LODDS). METHODS Four cohorts with a total of 2,309 gastric cancer patients were enrolled. For cohort 1 and 2, prognostic significance of each method by disease-specific survival was analyzed using Akaike and Bayesian information criterion (AIC and BIC). RESULTS The total LNs in four cohorts significantly differed [median (range), 28 (6-97) in cohort 1, 37 (8-120) in cohort 2, 48 (7-122) in cohort 3, and 54 (4-221) in cohort 4; p<0.001]. The numbers of negative LNs increased with increase of total LN (p<0.001), but the numbers of metastatic LNs did not increase from cohort 1 to 4. MLR and LODDS in four cohorts had decreasing tendency with increase of total LNs in each pT3 and pT4 category (p<0.001), while the numbers of metastatic LNs did not differ significantly in any pT category (p>0.05). The AIC and BIC varied according to different cut-off values for MLR; model by cut-offs of 0.2 and 0.5 being better for cohort 1, while cut-offs 0.1 and 0.25 was better for cohort 2. CONCLUSION Our study showed that the number of metastatic LNs did not increase with maximal pathologic examination of regional LNs. AJCC 7th system is suggested as the simplest method with single cut-off value, but prognostic significance of MLR may be influenced by various cut-offs.