Comparison of neoadjuvant regimens for resectable gastroesophageal junction cancer: a systematic review of randomized clinical trials across three decades

Background: The optimal perioperative treatment for adenocarcinoma of gastroesophageal junction (GEJ) tumor remains uncertain. The systematic review aims to assess the best neoadjuvant modality, namely chemotherapy (CT) versus chemoradiotherapy (CRT) based on randomized controlled trials (RCTs) for resectable gastric, esophageal and GEJ tumors. Methods: We performed a comprehensive PubMed database and Cochrane Library search to identify relevant RCTs related to neoadjuvant treatment for resectable GEJ adenocarcinoma. We included all published RCTs (phase 2 or 3) that tested specific neoadjuvant therapies (CT or CRT) if the patient population included GEJ tumors. We applied the Version 2 Cochrane risk-of-bias tool (RoB 2) to all the eligible studies. Outcomes examined included R0 resection and pathological response based on intention-to-treat (ITT) analysis, surgical outcomes, notable adverse events, and overall survival (OS). Each randomized group of every study was noted to be neoadjuvant CRT, CT, or surgery alone in order to compare the outcomes among these treatment approaches. Results: We identified 25 RCTs with 7,855 patients published from 1996 to 2019. Seven studies tested preoperative CT versus surgery alone, 7 tested preoperative radiotherapy (RT) or CRT versus surgery alone, 4 tested preoperative RT or CRT versus preoperative CT, and 7 tested other combinations. The R0 resection ranged 47-100% and the 3-year OS ranged 6-66.1% in all the study arms. In an exploratory analysis, CRT strategies showed a superior R0 resection rate [80.2%; 95% confidence interval (CI): 79.8-80.6%] to surgery alone (60.9%; 95% CI: 60.4-61.3%; P<0.01) and to preoperative CT (63.9%; 95% CI: 63.6-64.2%; P<0.01). When comparing 3- and 5-year OS, improvement was noted when comparing CRT to surgery alone (P<0.01), and perioperative CT to surgery alone (P<0.01), but no definite difference was noted between CRT versus CT. Discussion: Preoperative CRT showed improvement in R0 resection rate to surgery alone and preoperative CT. However, there is no significant difference in OS between CRT and CT. Both neoadjuvant strategies remain clinically meaningful options for patients with resectable GEJ tumors. Lack of patient-level data and inconsistent reporting of key outcomes across studies were the main limitations of our study.