The review question was clear and the inclusion criteria reported. Efforts were made to find published studies and no language restrictions were applied, but unpublished studies were not sought so there was a possibility that relevant trials could have been missed. However, no evidence of publication bias was identified. The authors did not report how many reviewers were involved in the study selection, quality assessment and data extraction, so reviewer bias and error was possible.
The authors reported overall score of the Jadad scale for trial quality, but full details were not reported which made it difficult to determine the reliability of the included trials. Details of the trial study characteristics were not reported, which made it difficult to assess the different cancer stage and grade of patients between trials. Appropriate methods were used to pool data and assess heterogeneity; some of the statistically significant outcomes showed evidence of heterogeneity.
The authors' conclusions appear to follow from the results, but should be viewed with caution due to small numbers of patients and lack of clarity about included trial quality.