Valenti 2008.

Methods	Study design: prospective cohort study
Participants	Country: UK. Number eligible: 40. Number excluded: 0 (0%). Number analysed: 40. Average age: 67 years. Females: 8 (20%). Stage I: not stated Stage II: not stated Stage III: not stated Stage IV: not stated Squamous cell carcinoma: 9 (22.5%). Adenocarcinoma: 28 (70%). Study design: Prospective cohort study with contemporary controls Total follow‐up in months: not stated ASA: ASA I or II: 12 versus 17; ASA III or IV: 4 versus 7 Location: lower third Inclusion criteria Patients undergoing transhiatal oesophagectomy for oesophageal cancer
Interventions	Group 1: laparoscopic transhiatal oesophagectomy (N = 16). Further details: number of ports ‐ 5; minilaparotomy ‐ 7 cm incision; drain use ‐ not stated. Group 2: open transhiatal oesophagectomy (N = 24). Further details: incision size ‐ not stated; drain used‐ not stated.
Outcomes	The outcomes reported were short‐term mortality and number of lymph nodes harvested.
Notes	Proportion of people with cancer: 93% (remaining patients had high grade dysplasia) Conversion: 0/16 (0%)
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 stage of the tumours)
Bias due to selection of participants to intervention and control	Unclear risk	No information Comment: Method of selection of participants to intervention and control was based on surgeon's preference.
Bias due to differences in co‐interventions which were different between the groups	Unclear risk	No information Comment: 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	High risk of bias Quote: "No blinded assessors (author replies)".
Bias due to missing data	Low risk	Low risk of bias Quote: "No patients excluded from analysis (author replies)".
Bias in selection of the reported findings	High risk	Serious risk of bias Comment: Morbidity was not reported.