Is ypN Sufficient to Stage Gastric Cancer Patients After Neoadjuvant Chemotherapy?

The accuracy of the eighth American Joint Committee on Cancer (AJCC) ypTNM staging system on the prognosis of gastric cancer patients after neoadjuvant chemotherapy is controversial. This study aimed to evaluate staging systems using the log odds of positive lymph nodes (LODDS) and the lymph node ratio (LNR) evaluation. We evaluated a case series of 45 GC patients who underwent radical gastric resection after neoadjuvant therapy in a single western center. The median age was 65 years old. The men/women ratio was 1.5. Data collection was conducted from January to December 2023 with a median follow-up of 76 months. Both 5- and 10-year overall survival (OS) and 5- and 10-year disease-free survival (DFS) were analyzed. We also evaluated the survival prognostic impact of ypN, yLNR, and yLODDS staging systems. The 5y-OS of the different pN staging categories was, respectively, pN0 90%, pN1 71.43%, pN2 50%, and pN3 46.87%. The 5y-OS of the different LNR staging subgroups was, respectively, LNR0 90%, LNR1 80%, LNR2 66.67%, and LNR3 27.71%. The 5y-OS of the different LODDS staging categories was, respectively, LODDS1 85.71%, LODDS2 77.78%, LODDS3 66.67%, and LODD4 27.71%. Instead, the 10y-OS in the ypN group was, respectively, N0 90%, N1 53.57%, N2 50%, and N3 46.87%. The 10y-OS in LNR group was LNR0 90%, LNR1 80%, LNR2 50%, and LNR3 27.71%, and the 10y-OS in LODDS classification was LODDS1 85.71%, LODDS2 77.78%, LODDS3 50%, and LODD4 27.71%. We did not find a statistical difference in DFS according to the pN staging system (p = 0.12). On the contrary, we showed a statistically significant difference in 5 and 10y-DFS according to LNR and LODDS staging categories (p = 0.018 and p = 0.026, respectively). The 5 and 10y-DFS in the different LNR categories were, respectively, LNR0 80.8% and 80.8%, LNR1 75% and 75%, LNR2 64.81% and 42.88%, and LNR3 41.56% and 41.56%. The 5 and 10y-DFS of the different LODDS categories were, respectively, LODDS1 72.92% and 72.92%, LODDS2 83.33% and 83.33%, LODDS3 68.57% and 50.67%, and LODD4 41.56% and 41.56%. Many survival prognostic factors were analyzed as age, tumor site, tumor size, surgery, T categories, histological subtype groups, number of metastatic nodes, N ratio, and LODDS. After, we compared the three lymph node staging systems ypN, yLNR, and yTLM. The metastatic lymph node ratio could represent a more reliable staging system regardless of the examined number of lymph nodes. On the other hand, LODDS can provide more information than pN. The pN only measures the absolute number of positive lymph nodes and does not provide additional information. In addition, LODDS is more acceptable than pN because it contains more information related to the status of lymph nodes. Our results confirm that a novel established staging system based on LODDS and lymph node ratio could offer a good survival stratification in GC patients receiving NAC.