Diffuse Type Advanced Gastric Cancer Showing Dismal Prognosis is Characterized by Deeper Invasion and Emerging Peritoneal Cancer Cell : The Latest Comparative Study to Intestinal Advanced Gastric Cancer

Background/Aims: Diffuse type advanced gastric cancer (D-AGC) is highly malignant disorder with dismal prognosis, however the causative attribution explaining such malignancy remains fully unexplained as compared to intestinal type AGC (I-AGC). Methodology: We examined the archive of 232 AGC with cytology test (CY) but no distant metastasis, who underwent gastrectomy in Kitasato University Hospital in order to reveal the prognostic significance of D-AGC in a multivariate approach. Results: D-AGC occupied 68% (157/232) among AGC, and showed poorer prognosis than I-AGC (p= 0.024). Multivariate prognostic analysis revealed that independent prognostic factors for AGC are CY (p<0.0001), pN (p=0.0068), pT (p=0.015), and age (p=0.012), and that histology was eliminated, suggesting that histology itself does not represent high malignancy within the identical stage. D-AGC was significantly associated with younger age (p= 0.018), female preponderance (p=0.006), advanced pT (p=0.0002), advanced pN (p=0.016), and positive CY factors (p=0.032), among which negative prognostic factors were pT, pN, and CY factors. Multivariate logistic regression analysis elucidated that both pT (serosal exposure, p=0.013) and CY (p= 0.034) factors were finally remnant independent predictors for D-AGC among the 3 univariate negative prognostic factors, but that pN was not. Intriguingly, age could be an independent prognostic factor only in D-AGC. Conclusion: Our research revealed for the first time that more dismal prognosis of D-AGC than I-AGC could be explained by propensity of deeper invasion and emerging peritoneal cancer cell, and histology itself did not have a prognostic value, hence indicating that present staging system works properly even in D-AGC as well as I-AGC. We must identify its molecular mechanism of both invasion and emerging peritoneal disease of D-AGC in order to improve the prognosis.