Background. Little data on directly comparing chemoradiotherapy with observation has yet been published in the setting of adjuvant therapy for resected gastric cancer who underwent D2 lymphadenectomy. The present indirect comparison aims to provide more evidence on comparing the two approaches. Methods. We conducted a systematic review of randomized controlled trials, extracted time-to-event data using Tierney methods (when not reported), and performed indirect comparison to obtain the relative hazards of adjuvant chemoradiotherapy to observation on overall and disease-free survival. Results. seven randomized controlled trials were identified. Three trials compared adjuvant chemoradiotherapy with adjuvant chemotherapy, and 4 trials compared adjuvant chemotherapy with observation. Using indirect comparison, the relative hazards of adjuvant chemoradiotherapy to observation were 0.43 (95% CI: 0.33–0.55) in disease-free survival and 0.52 (95% CI: 0.38–0.71) in overall survival for completely resected gastric cancer with D2 lymphadenectomy. Conclusions. Postoperative chemoradiotherapy can prolong survival and decrease recurrence in patients with resected gastric cancer who underwent D2 gastrectomy. Molecular biomarker might be a promising direction in the prediction of clinical outcome to postoperative chemoradiotherapy, which warranted further study. 1. Introduction Gastric cancer is the third leading cause of cancer-related death among men and the fifth among women in the worldwide [1]. The primary curative treatment of gastric carcinoma is surgical resection [2]. Complete resection with adequate margins is widely considered as a standard goal, whereas the extent of lymph node dissection remains controversial. Irrespective of the surgical procedure used for the treatment of gastric cancer, the effectiveness of surgical resection is poor; about 60% eventually have local relapse or distant metastases after curative resection [3]. The high rate of relapse or distant metastases after resection make it important to consider adjuvant treatment for patients with resected gastric cancer. The INT-0116 trial [4, 5], the largest phase III trial comparing chemoradiotherapy versus observation, shows that adjuvant chemoradiotherapy prolonged overall survival (OS) and relapse-free survival (RFS). In this trial, 10% of the patients underwent D2 dissection, suggesting that chemoradiotherapy might be only compensating for inadequate surgery. Therefore, the role of chemoradiation therapy after D2 dissection has been questioned. Two retrospective studies demonstrated that
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