P-241 Metastatic lymph node ratio as an addition to the nodal evaluation of TNM staging: A new sight for prevention of stage migrations

Abstract

TNM staging is a routine grading system for gastric cancer, but the survival of gastric cancer gets better with early diagnoses and a better management with the correlation of oncology and general surgery departments. Making additions to TNM classification is important in terms of clarifying surveillance and preventing stage migrations. The purpose of this study was to evaluate the metastatic lymph node ratios in locally advanced gastric cancer patients who have undergone curative gastrectomy with D2 dissection. From January 2011 to December 2015, 341 patients were diagnosed with gastric adenocarcinoma and 226 patients underwent curative gastrectomy in our hospital. As curative gastrectomies with R0 resection and patients without distant metastasis were included in the study, palliative surgeries, R1-R2 resections, emergent surgeries and surgeries with insufficient lymph node dissection are excluded. From 226 patients, 193 patients whose tumor was not T1 and whose both preoperative and postoperative data were present were included in the study. In particular, lymph node metastasis was not present in 81 patients. The ratio between the number of metastatic lymph nodes and total number of dissected lymph nodes was analysed to evaluate their influences on the disease outcome. Patients were divided into three groups according to the ratio (NR) between metastatic lymph nodes and total nodes dissected. The number of metastatic lymph nodes ranged from 0 to 43 (mean, 6.77±4.82) and the number of dissected total lymph nodes ranged from 15 to 93 (mean 27.13±6.91). There was no significant correlation between numbers of metastatic and dissected lymph nodes (p:0.142). Survival of patients at 5 years regardless of their stage was 54.1%, with a median survival of 23.24±4.18 months. According to regional nodal status (N) of the 8th edition of the AJCC, patients with N0 (n=81), pN1 (n=24), pN2 (n=31) and pN3 (n=67) showed survival rates at 5 years of 81.7%, 75.0%, 45.2% and 40.3%, respectively (p=0.009). Patients were stratified into NR0 (ratio 0%), NR1 (ratio 1-49%) and NR2 (ratio >50%). Their survival rates at 5 years were 81.7%, 53.5% and 36.1%, respectively (p=0.008). Metastatic lymph node ratio is an independent prognostic factor in survival regardless of the number dissected in the surgical process. The metastatic lymph node ratio has a more beneficial effect on disease-free and overall survival than the number of metastatic lymph nodes. If D2 dissection is done, metastatic lymph node ratio should be added to pathological TNM staging for a better foresight and for the prevention of stage migrations.