Table 1.

Characteristics of included studies (ITT: intention-to-treat)

Study ID (author, yr)	Design	Methods	Patients	Interventions	Outcomes	Notes
Jiang et al 2000[36]	RCT	Single center, parallel group, not clear about the method of randomization	Histologically proved curable advanced gastric cancer	D2 vs D2+	Post-operative morbidity and mortality; Operation time	Regional lymph nodes were classified according to 1th English edition 1995[32]
Sano et al 2004[37] and Sasako et al 2008[39] Kodera et al 2005[38]	RCT	Multicenter, parallel group, computer stratified randomization	Histologically proved advanced and curable gastric cancer	D2 vs D2+	Post-operative morbidity and mortality; Operation time; Blood loss during operation; Five-year survival rate	ITT was used in result analysis; Regional lymph nodes were classified according to 1th English edition 1995[32]
Yonemura et al 2006 and 2008[40,41]	RCT	Multicenter, parallel group, computer randomization	Younger than 75-yr old, histologically proved advanced and curable gastric cancer	D2 vs D2+	Post-operative morbidity and mortality; Operation time; Blood loss during operation; Five-year survival rate	Sample size was calculated before trials
Kulig et al 2007[42]	RCT	Multicenter, parallel group, simple computer randomization.	Histologically proved curable gastric adenocarcinoma	D2 vs D2+	Post-operative morbidity and mortality; Operation time; Blood loss during operation	Regional lymph nodes were classified according to 2nd English edition 1998[31]; ITT was used in result analysis
Maeta et al 1999[43]	non-RCT	Single center, parallel group, without randomization	Histologically proved advanced gastric cancer, younger than 75-yr old	D2 vs D2+	Post-operative morbidity and mortality; Operation time; Blood loss during operation	In D4 group, lymph nodes (a1, a2, b1 and b2) were all removed; Sample size was smaller than that calculated before study
Bostanci et al 2004[44]	non-RCT	Single center, parallel group, prospective study without randomization	Histologically proved gastric cancer	D2 vs D2+	Post-operative morbidity and mortality; Operation time	Surgical procedure was not very clearly described in the article
Kunisaki et al 2006[45]	non-RCT	Multicenter, parallel group, retrospective analysis	Curable advanced gastric cancer proved by histology	D2 vs D2+	Post-operative morbidity and mortality; Operation time; Blood loss during operation; Five-year survival rate	Data about length of post-operative hospital stay were obtained from the author
Hu et al 2009[46]	non-RCT	Single center, parallel group, retrospective analysis	Histologically proved curable gastric cancer	D2 vs D2+	Post-operative morbidity and mortality; Operation time; Five-year survival rate	In D4 group, lymph nodes (a1, a2 and b1) were dissected

RCT: Randomized controlled trial.