Impact of microsatellite status on negative lymph node count and prognostic relevance after curative gastrectomy.

ABSTRACT

BACKGROUND AND OBJECTIVES: The impact of microsatellite instability-high (MSI-H) phenotype on lymph node yield after lymphadenectomy has never been discussed in gastric cancer (GC). In this study, we aimed to assess the association of microsatellite status with negative lymph node count (NLNC) as well as its prognostic value. METHODS: We retrospectively analyzed 1491 GC patients and divided them into two groups MSI-HGC (n = 141 [9.5%]) and microsatellite stability (MSSGC ) (n = 1350 [90.5%]). The NLNC and survival data were compared between the two groups. The log odds of positive lymph nodes (LNs) to negative LNs and the target lymph node examined threshold (TLNT) were calculated in both groups. RESULTS: A statistically significant difference was found in median NLNC (26 vs. 23, p < .001) between MSI-HGC and MSSGC patients. MSI status was an independent factor for NLNC (p < .001). NLNC showed positive prognostic value for cases with metastatic lymph node (LN+ ) in both MSI-HGC and MSSGC groups. The TLNT(90%) for MSI-HGC and MSSGC were 33 and 26, respectively. CONCLUSIONS: MSI-HGC was associated with higher NLNC in GC patients and this was independent of the presence of LN+ . However, more LNs are needed during pathological examination to capture LN+ cases in MSI-HGC.