Predictive factors for histological response to neoadjuvant therapy in gastric adenocarcinomas.

BACKGROUND: Perioperative chemotherapy is the standard curative treatment for resectable gastric adenocarcinoma, significantly improving both overall and recurrence-free survival. The histological response to neoadjuvant therapy is a critical prognostic factor, commonly assessed through grading systems such as Mandard's tumor regression grade (TRG). AIMS: The aim of the study was to identify predictive factors for histological response to neoadjuvant therapy in gastric adenocarcinoma. METHODS: A retrospective study was performed on patients with gastric adenocarcinoma who underwent surgery following neoadjuvant chemotherapy, from 2015 to 2020. The histological response was evaluated using Mandard TRG, which includes five grades (1-5), based on the proportion of residual viable tumor cells and fibrosis. Grades 1-3 were considered a response, and Grades 4 and 5 were considered no response. Students' t-test, chi-squared test, and multivariate logistic regression were used, with significance set at p<0.05. RESULTS: Forty patients were included (male-to-female ratio 2.64, mean age 63 years). Histological response (TRG 1-3) was observed in 48%, while 52% showed no response (TRG 4-5). Univariate analysis showed significant correlations between histological response and tumor size >38 mm (p=0.03), differentiation (p=0.02), parietal wall invasion, absence of nodal involvement (both p<0.001), pathological tumor, node, and metastasis stage (p<0.001), and absence of vascular and perineural invasion (both p=0.001). Multivariate analysis identified parietal wall invasion (odds ratio=2.351, p=0.022) and absence of lymph node metastases (odds ratio=1.491, p=0.01) as independent predictive factors. CONCLUSIONS: Parietal wall invasion and absence of nodal metastases are predictive of histological response to neoadjuvant therapy in gastric adenocarcinoma.