[Efficacy of maintenance therapy with or without pembrolizumab in patients with advanced gastric cancer after first-line chemotherapy].

Objective: To observe the efficacy of maintenance therapy with or without Pembrolizumab in patients with advanced gastric cancer after first-line chemotherapy. Methods: A total of 182 patients with advanced gastric cancer who received first-line induction therapy in our hospital from August 2021 to August 2023 were retrospectively included. According to the maintenance treatment strategy, the patients were divided into two groups. Patients received single-agent maintenance therapy with Pembrolizumab were in the single-agent group, and patients received combined maintenance therapy with Pembrolizumab and chemotherapy were in the combination group. The follow-up period was until October 2025. The levels of tumor-related markers, immune function indexes, tumor response, progression-free survival, overall survival, and adverse reactions within 1 year of maintenance treatment between the two groups were compared. Kaplan-Meier method was used to estimate median progress free survival (PFS) and overall survival (OS), and the log-rank test was used to compare survival differences between groups. Multivariate Cox proportional hazards regression model was used to analyze the impact of different maintenance treatment strategies on survival. Results: There were 98 cases in the monotherapy group, with an age of (64.81±7.55) years, and 84 cases in the combination therapy group, with an age of (64.55±8.47) years. The results of repeated measures analysis showed that during maintenance treatment, the levels of tumor markers such as carcinoembryonic antigen, cancer antigen(CA)125, CA199 in both the combination and monotherapy groups exhibited a decreasing trend, with a more pronounced decrease in the combination group (all P<0.05). Both the intergroup differences and the change trend differences in immunogloblin (Ig)A, IgG, and CD4+levels were statistically significant (all P<0.05); the monotherapy group remained relatively stable for these indicators, while the combination group showed a decreasing trend. The change trend differences in CD3+and CD8+levels between the two groups were statistically significant (all P<0.05), but the intergroup differences were not statistically significant (all P>0.05). Neither the intergroup difference nor the change trend difference in IgM level was statistically significant (all P>0.05). The RR of the combination group and the single drug group were 14.29% and 7.14%, and the DCR were 36.90% and 24.49%, respectively, with no significant difference (P>0.05). The median PFS in the combination group and the single drug group were 9.24 (95%CI: 8.19-10.29) and 8.92 (95%CI: 7.95-9.89) months, respectively, and the median OS in the combination group and the single drug group were 14.58 (95%CI: 12.65-16.51) and 16.04 (95%CI: 14.19-17.89) months, respectively, with no statistically significant difference (P>0.05). After adjusting for confounding factors by multivariate Cox regression analysis, treatment grouping was not an influencing factor for PFS or OS (all P>0.05). The incidence or severity of gastrointestinal reactions, leukopenia, hand foot syndrome, liver and kidney dysfunction, and thyroid dysfunction in the combination group were higher than those in the single drug group (all P<0.05). Conclusions: In patients with advanced gastric cancer after first-line chemotherapy for disease control, there is no statistically significant difference in the efficacy of maintenance therapy with or without Pembrolizumab combined with chemotherapy, and it can reduce the cumulative toxicity caused by continuous chemotherapy.