Oncologic Benefit of Adjuvant Chemoradiation after D2 Gastrectomy: A Stepwise Hierarchical Pooled Analysis and Systematic Review

Our study aimed to evaluate the benefits of chemoradiotherapy (CRT) after D2 gastrectomy, as compared to adjuvant chemotherapy, alone. PubMed, MEDLINE, Embase, and the Cochrane Library were systematically searched. We applied stepwise analyses that enabled the evaluation of data from randomized controlled trials (RCTs), balanced studies, and all studies separately and in a hierarchical manner. Thirteen controlled studies, including six RCTs involving 2603 patients, were included. Overall pooled analysis revealed a disease-free survival benefit of CRT (odds ratio (OR): 1.264, p = 0.053), which was more evident in the subgroup analysis of RCTs (OR: 1.440, p = 0.006) and balanced studies (OR: 1.417, p < 0.001). Overall survival was insignificantly different in the overall pooled analysis (OR: 1.124, p = 0.347). However, the difference was marginally significant in the subgroup analysis of balanced studies (OR: 1.279, p = 0.055) and significant in the subgroup analysis of studies involving stage ≥III patients only (OR: 1.663, p = 0.005). Locoregional recurrence (LRR) reduction was noted in the overall pooled analysis (OR: 0.559, p = 0.012; pooled rate: 11.3% vs. 18.1%) and was more robust in the subgroup analyses. Grade ≥3 leukopenia was higher in the CRT arm (OR: 1.387, p = 0.004; pooled rate: 26.4% vs. 15.7%). CRT after D2 gastrectomy should be applied for patients with high risk of LRR (e.g., stage ≥ III), along with efforts to reduce leukopenia.