# Adjuvant Chemotherapy and Chemoradiotherapy in Gastric Cancer: Prognostic Determinants and Real-World Survival Outcomes

## TL;DR

This study compares adjuvant chemotherapy and chemoradiotherapy in gastric cancer patients, finding that survival differences disappear after adjusting for baseline differences, with advanced disease features as key prognostic factors.

## Contribution

The study provides real-world survival data and identifies independent prognostic factors after adjusting for treatment selection bias in gastric cancer patients.

## Key findings

- Unadjusted survival favored chemotherapy alone, but differences disappeared after adjusting for baseline differences.
- Advanced T–N stage, vascular invasion, and positive margins were identified as independent prognostic factors.
- Subgroup analyses showed no significant treatment interactions after adjustment.

## Abstract

Objective: The role of adjuvant chemoradiotherapy (CRT) following curative gastrectomy remains controversial, especially in the context of D2 dissection. This research evaluated survival indicators through an analysis of previous observational studies and it evaluated treatment outcomes between patients who underwent CRT and those who received CT as their sole therapy. Methods: The researchers performed a non-randomized retrospective cohort study which analyzed 206 patients who underwent R0–R1 resection for gastric adenocarcinoma and received either adjuvant CRT (n = 107) or CT alone (n = 99). A Kaplan–Meier analysis together with Cox regression methods were used to evaluate survival outcomes of patients. Inverse probability of treatment weighting (IPTW) was applied to adjust for baseline differences between groups at the beginning of the study. The median follow-up was 52.0 months. Results: The baseline characteristics differed markedly between groups, with CRT patients showing higher rates of T4 tumors (34.6% vs. 22.2%), N3 disease (47.7% vs. 26.3%), vascular invasion (72.9% vs. 50.5%), and R1 resection (10.3% vs. 1.0%). Unadjusted survival favored CT alone (median DFS 81.7 vs. 103.9 months; median OS 86.2 months vs. not reached). These differences lost significance after IPTW adjustment (DFS: HR 1.18, p = 0.428; OS: HR 1.24, p = 0.336). T3–T4 stage, N2–N3 nodal status, vascular invasion, and positive margins emerged as independent prognostic factors. Subgroup analyses revealed no treatment interactions (all p > 0.05). Conclusions: The research used a retrospective study design which showed substantial differences between treatment groups at the beginning of the study. The survival results that showed better outcomes for CT alone became attenuated after the researchers applied propensity score adjustment to adjust for confounding from treatment selection. The study established that advanced T–N stage, vascular invasion, and positive margins were identified as independent prognostic factors. The research results are hypothesis-generating and require randomized controlled trials to establish the exact difference in effectiveness between different treatments.