Maas 2012.

Methods	Study design: retrospective cohort study
Participants	Country: Netherlands. Number eligible: 100. Post‐randomisation drop‐outs: 0 (0%). Number analysed: 100. Average age: 64 years. Females: 26 (26%). Stage I: 7(7%). Stage II: 31 (31%). Stage III: 62 (62%). Stage IV: 0(0%). Squamous cell carcinoma: 28 (28%). Adenocarcinoma: 69 (69%). Study design: Retrospective cohort study with historical control Total follow‐up in months: not stated ASA: ASA I or II: 38 versus 36; ASA III or IV: 12 versus 14 Location: lower third Inclusion criteria Patients undergoing transhiatal oesophagectomy for distal oesophageal cancer Exclusion criteria Patients with colon interposition
Interventions	Group 1: laparoscopic transhiatal oesophagectomy (N = 50). Further details: number of ports ‐ 5; minilaparotomy ‐ 7 cm periumbilical incision); drain use ‐ not stated. Group 2: open transhiatal oesophagectomy (N = 50). Further details: incision size ‐ not stated; drain use ‐ not stated.
Outcomes	The outcomes reported were short‐term and long‐term mortality, morbidity, long‐term recurrence, length of hospital stay, positive resection margin, and number of lymph nodes harvested.
Notes	Proportion of people with cancer: 100% Conversion: 9/50 (18%)
Risk of bias
Bias	Authors' judgement	Support for judgement
Bias due to confounding	Unclear risk	No information Comment: There was no evidence of baseline differences between the groups. However, the sample size was not sufficient to identify baseline differences. In addition, not all confounding factors were listed in the baseline differences table (for example, no information was presented on the differences in the size of the tumours)
Bias due to selection of participants to intervention and control	Unclear risk	Moderate risk of bias Comment: This was a consecutive series of laparoscopic oesophagectomies where the surgeon performed all transhiatal oesophagectomies laparoscopically after January 2001.
Bias due to differences in co‐interventions which were different between the groups	Unclear risk	No information Comment: A historical control was used. It was not clear there were other differences in care of the patient apart from the intervention and control.
Bias in the measurement of outcomes	High risk	Critical risk of bias Comment: The assessment of the patients was not done blinded (author replies).
Bias due to missing data	Low risk	Low risk of bias Comment: All patients were included in the analysis.
Bias in selection of the reported findings	Low risk	Low risk of bias Comment: Mortality and morbidity were reported adequately.