Evaluating peritoneal elastic laminal invasion to improve stratification of patients with pT3 gastric cancer.

[BACKGROUND] Elastic laminal invasion (ELI), defined as tumor invasion beyond the peritoneal elastic lamina, may affect gastric cancer (GC) prognosis, though limited data exist on this relationship.

[METHODS] We retrospectively reviewed representative pathological slides from 396 patients with pT3 or pT4a GC who underwent curative resection to assess the association between ELI and relapse-free survival (RFS) and overall survival (OS).

[RESULTS] The 5-year RFS of pT3 GC with negative ELI was 85.9%, which was better than the 55.9% of that of ELI-positive pT3 (P < 0.001) or pT4a (51.3%) GC (P < 0.001). Similarly, the 5-year OS of ELI-negative pT3 GC was 90.4%, while the corresponding values for ELI-positive pT3 and pT4a were 67.0% (P < 0.001) and 63.6% (P < 0.001), respectively. Multivariate analysis revealed that the most significant prognostic factors for RFS were pT factors (i.e., pT3 with ELI/pT4), tumor size (≥ 80 mm), and nodal metastasis. We subdivided our cohort of patients with pathological stage II (pT3N0, pT3N1) GC into ELI-negative and ELI-positive subgroups, and found that the ELI-negative ones had better RFS percentages than those who were ELI-positive or stage III (P = 0.002 and P < 0.001, respectively).

[CONCLUSIONS] ELI-positive pT3 GC has a worse prognosis than its ELI-negative counterpart, comparable to that of pT4a. These findings suggest a need to revisit the pT grading system in GC.