The identification of prognostic biomarkers (PB) for gastric cancer (GC) patient selection is compelling to improve survival outcomes. Microsatellite instability (MSI) is related with a positive prognostic effect in resected GC, whereas perioperative chemotherapy (CT) is detrimental. In metastatic MSI GC, immunotherapy (IT) with anti-PD1/PDL-1 drugs has shown promising results. Nevertheless, in early stages (ES), data on the relation between MSI, clinic-pathological (CP) features, PDL-1 expression and overall survival (OS) remain sparse, especially in Western population. In this study, the prognostic role of MSI status, CP features and PDL-1 status in a large cohort of Italian GC patients (pts) was examined.
CP data of 148 consecutive stage I-III GC pts resected in Cremona Institute between 2010 and 2014 (mostly chemo and/or radio-naive) were collected. MSI analysis was performed on tissue samples for all cases by polymerase chain reaction. PDL-1 expression, evaluated by immunohistochemistry, was assessed in MSI group. Differences between subgroups were evaluated with Chi-square test; Kaplan-Meier method and Long Rank test were used to calculate OS.
Female sex (p = 0.012), earlier TNM stages (p = 0.011) and lower nodal involvement (p = 0.029) significantly correlated with MSI status. MSI is significantly associated with prolonged survival (p < 0.001), with an advantage of 28.6 months in OS compared to the microsatellite stable (MSS) group. Most MSI pts (71%) expressed PDL-1. Although not statistically significant, MSI pts without PD-L1 expression showed a better trend in OS compared with MSI GC pts expressing PDL-1 and with MSS group.Table: 688P
Main CP differences between MSS and MSI groups and survival outcomes
|MSS 110 (79.7%)||MSI 38 (25.7%)||p|
|SEX M F||77 (70) 33 (30)||18 (47.4) 20 (52.6)||0.012|
|STAGE (TNM) I II III||19 (17.3) 26 (23.6) 65 (31.6)||13 (34.2) 13 (34.2) 12 (31.6)||0.011|
|NODAL METASTASES NO YES||26 (23.6) 84 (76.4)||16 (42.1) 22 (57.6)||0.029|
MSI is an independent PB in GC and identifies a subset of pts with better OS and specific CP characteristics, including high expression of PDL-1. MSI could be a promising biomarker to select pts for CT vs IT in ES of GC.
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All authors have declared no conflicts of interest.