Background: The assessment of human epidermal growth factor receptor 2 (HER2), microsatellite instability (MSI) and programmed cell death-ligand 1 (PD-L1) expression is relevant for the selection and effectiveness of targeted therapy in gastric cancer (GC).
Objective: We aimed to investigate the clinicopathological characteristics and prognosis of GC patients according to these profiles.
Methods: GC patients who underwent gastrectomy with D2 lymphadenectomy were eligible. HER2, MSI status and PD-L1 expression were analyzed by immunohistochemistry (IHC). Patients were grouped as follows: HER2+ group, immunotherapy (IT) group (MSI and/or PD-L1+), and non-targeted therapy (NTT) group (stable microsatellite and HER2/PD-L1-).
Results: Among 282 patients, 50 (17.7%) were HER2+ and 79 (28%) MSI/PD-L1+. Fifteen had HER2+ and MSI/PD-L1+, while 168 (59.6%) were in the NTT group. HER2+ GCs were related to male gender (p = 0.007), intestinal type (p = 0.001) and less advanced pTNM stage (p = 0.029). Older age (p = 0.003), subtotal gastrectomy (p = 0.025), intestinal type (p = 0.008), pN0 status (p = 0.002) and less advanced pTNM stage (p = 0.001) were associated with the IT group. IT GC had better disease-free survival (DFS) and overall survival than the NTT group (p = 0.015 and p = 0.027, respectively). Concerning patients eligible for the standard adjuvant therapy, the treatment impacted positively on DFS for HER2+ and NTT groups (p = 0.003 and p = 0.042, respectively). No difference in DFS was seen between IT patients who received perioperative/adjuvant therapy and those treated only with surgery (p = 0.160).
Conclusions: GC patients who exhibited markers that can serve as an indication for known targeted therapy represent 40.4% of cases. The IT group was associated with a better prognosis. No benefit with standard adjuvant treatment appears to be achieved in MSI/PD-L1+ GCs.