Pathologic Outcomes of Laparoscopic vs Open Mesorectal Excision for Rectal Cancer: A Systematic Review and Meta-analysis.

Importance: Rectal resection with mesorectal excision is the mainstay treatment for rectal cancer.

Objective: To review and analyze the evidence concerning the pathologic outcomes of laparoscopic (LRR) vs open (ORR) rectal resection for rectal cancer.

Data Sources: The Cochrane Central Register of Controlled Trials, MEDLINE (through PubMed), EMBASE, Scopus databases, and clinicaltrials.gov were searched for randomized clinical trials (RCTs) comparing LRR vs ORR.

Study Selection: Only RCTs published in English from January 1, 1995, to June 30, 2016, that compared LRR with ORR for histologically proven rectal cancer in adult patients and reported pathologic outcomes (eg, positive circumferential resection margin, and complete mesorectal excision) were eligible for inclusion. Of 369 records screened, 14 RCTs were selected for the qualitative and quantitative analyses.

Data Extraction and Synthesis: Two independent reviewers performed the study selection and quality assessment. Random-effects models were used to summarize the risk ratio (RR) and mean differences.

Main Outcomes and Measures: The rate of positive circumferential resection margin (CRM), defined as 1 mm or less from the closest tumor to the cut edge of the tissue, and the quality of mesorectal excision (complete, nearly complete, or incomplete).

Results: The meta-analysis included 14 unique RCTs with 4034 unique patients. Of 2989 patients undergoing rectal resection, a positive CRM was found in 135 (7.9%) of 1697 patients undergoing LRR and 79 (6.1%) of 1292 patients undergoing ORR (RR, 1.17; 95% CI, 0.89-1.53; P = .26; I2 = 0%) in 9 studies. A noncomplete (nearly complete and incomplete) mesorectal excision was reported in 179 (13.2%) of 1354 patients undergoing LRR and 104 (10.4%) of 998 patients undergoing ORR (RR, 1.31; 95% CI, 1.05-1.64; P = .02; I2 = 0%) in 5 studies. The distal resection margin involvement (RR, 1.12; 95% CI, 0.34-3.67; P = .86), the mean number of lymph nodes retrieved (mean difference, 0.05; 95% CI, -0.77 to 0.86; P = .91), the mean distance to the distal margin (mean difference, 0.01 cm; 95% CI, -0.12 to 0.15 cm; P = .87), and the mean distance to radial margins (mean difference, -0.67 mm; 95% CI, -2.16 to 0.83 mm; P = .38) were not significantly different between LRR and ORR. The risk for bias was assessed as low in 10 studies, high in 3, and unknown in 1. The overall quality of the evidence emerging from the literature was rated as high.

Conclusions and Relevance: Based on the available evidence, the risk for achieving a noncomplete mesorectal excision is significantly higher in patients undergoing LRR compared with ORR. These findings question the oncologic safety of laparoscopy for the treatment of rectal cancer. However, long-term results of the ongoing RCTs are awaited to assess whether these pathologic results have an effect on disease-free and overall patient survival.