Early antibiotic exposure does not affect prognosis in patients with advanced gastric cancer treated with PD-1...

To explore the prognostic impact of antibiotic exposure during programmed death receptor-1 (PD-1) inhibitor therapy in patients with advanced gastric cancer (AGC).

Data of 218 AGC patients treated with PD-1 inhibitors were retrospectively collected. The impact of antibiotic exposure in different time windows and other clinical factors on the prognosis of AGC patients was analyzed.

Antibiotic exposure prior to PD-1 inhibitor therapy (pATB) was significantly correlated with peritoneal metastasis (P = 0.007). Concurrent antibiotic exposure (cATB) was associated with different treatment types (P = 0.012) and ECOG PS (P < 0.001). In terms of prognosis, neither pATB nor cATB exposure significantly affected overall survival (OS) (P = 0.804, P = 0.324), whereas cATB exposure was a predictive factor for progression free survival (PFS) (P = 0.007). Treatment lines (P < 0.001) and cATB exposure (P = 0.027) were independent prognostic variables for predicting PFS according to multivariate Cox analysis. Furthermore, it was found that treatment lines (P = 0.004) and peritoneal metastasis (P = 0.002) were independent prognostic variables that predicted OS. However, in the sensitivity analysis, nine patients experienced varying degrees of delay in subsequent treatment after cATB exposure, leading to disease progression. Exclusion of these nine patients revealed that adjusted cATB exposure was not a prognostic factor for PFS in AGC patients (P = 0.074).

There is no evidence that antibiotics affect the long-term OS prognosis of AGC patients receiving PD-1 inhibitor therapy. Therefore, physicians should not delay PD-1 inhibitor combination treatment regimens in AGC patients who have recently received antibiotics.