Positive lymph node ratio as a nodal staging system to avoid stage migration between remnant and primary proximal gastric cancers.

Nodal staging of gastric cancer (GC) based on the number of positive lymph nodes (PLNs) is a robust prognostic factor. However, the number of retrieved lymph nodes in remnant GC (RGC) may be lower than in primary GC owing to variations in the extents of initial gastrectomy and lymphadenectomy. This study evaluated stage migration between RGC and primary proximal gastric cancer (PGC) and the clinical usefulness of the PLN ratio (PLNR) in mitigating stage migration. Among 4,142 patients who underwent gastrectomy, 91 with RGC and 768 with PGC at pStage I-III were retrospectively analyzed. A PLNR of 0.3 was the best-stratified prognosis (p < 0.001). Five-year survival in pN1-3 RGC was worse than in PGC, whereas pN0 showed no prognostic difference. PLNR stratification (0, < 0.3, and ≥ 0.3) effectively distinguished prognosis in patients with RGC (82.2, 46.6, 12.7%, respectively) and PGC (88.9, 63.4, 16.4%, respectively). High PLNR (≥ 0.3) was an independent prognostic factor in RGC (HR: 2.76, 95% CI: 1.06-7.17, p = 0.036), whereas pN stage was not. Prognostic stratification was reliable with at least five dissected lymph nodes. PLNR provides effective prognostic stratification in RGC and helps evaluate stage migration between RGC and primary PGC.