Non-invasive liquid biopsy based on transcriptomic profiling for early diagnosis of occult peritoneal metastases in locally advanced gastric cancer

Gastric cancer (GC) remains one of the leading causes of cancer-related death worldwide, especially in East Asian countries. Despite advances in treatment, patients with locally advanced gastric cancer (LAGC) still have a poor prognosis due to the high incidence of metastasis and recurrence. Peritoneal metastasis is particularly occult and difficult to detect by conventional imaging techniques at an early stage. Existing imaging methods lack high sensitivity and are difficult to detect early metastatic lesions. Although diagnostic laparoscopy has high sensitivity, it is invasive and difficult to use routinely. Therefore, innovative diagnostic methods are urgently needed. Transcriptomics methods can provide a comprehensive understanding of the biological state of cancer, especially showing potential in the early detection of GC and peritoneal metastasis. Our objective is to provide a more sensitive diagnostic method in the latent stage of peritoneal metastasis by identifying the RNA expression pattern of cancer cells. To investigate the RNA expression patterns of GC tissues with or without peritoneal metastasis, we performed RNA sequencing (RNA-seq) analysis on ribosomal RNA-depleted total RNA extracted from GC tissue samples of 17 GC patients (5 with peritoneal metastasis and 12 with primary lesions but without peritoneal metastasis).