Similarities and differences between study designs in short‐ and long‐term outcomes of laparoscopic versus open low anterior resection for rectal cancer: A systematic review and meta‐analysis of randomized, case‐matched, and cohort studies

AIM: Randomized controlled trials (RCT) are the gold standard in surgical research, and case‐matched studies, such as studies with propensity score matching, are expected to serve as an alternative to RCT. Both study designs have been used to investigate the potential superiority of laparoscopic surgery to open surgery for rectal cancer, but it remains unclear whether there are any differences in the findings obtained using these study designs. We aimed to examine similarities and differences between findings from different study designs regarding laparoscopic surgery for rectal cancer. METHODS: Systematic review and meta‐analyses. A comprehensive literature search was conducted using PubMed, Scopus, and Cochrane. RCT, case‐matched studies, and cohort studies comparing laparoscopic low anterior resection and open low anterior resection for rectal cancer were included. In total, 8 short‐term outcomes and 3 long‐term outcomes were assessed. Meta‐analysis was conducted stratified by study design using a random‐effects model. RESULTS: Thirty‐five studies were included in this review. Findings did not differ between RCT and case‐matched studies for most outcomes. However, the estimated treatment effect was largest in cohort studies, intermediate in case‐matched studies, and smallest in RCT for overall postoperative complications and 3‐year local recurrence. CONCLUSION: Findings from case‐matched studies were similar to those from RCT in laparoscopic low anterior resection for rectal cancer. However, findings from case‐matched studies were sometimes intermediate between those of RCT and unadjusted cohort studies, and case‐matched studies and cohort studies have a potential to overestimate the treatment effect compared with RCT.