Data extraction and quality assessment

Two reviewers reviewed each article independently and abstracted data from the articles in accordance with a standardized form. Disagreements were resolved through discussion, and when it the differences were not resolved, a third person made a final decision. The following data were extracted: the authors, publication years, study design, sample size, SR rate, risk factors (tumor location, tumor differentiation, T stage, LNM, paratracheal LNM, preoperative RT, post-operative RT, preoperative tracheotomy – POT), and pharyngoperistomal fistula. There is no widely accepted quality-assessment metric available for case series. Thus, the quality was evaluated using one of the forms issued by The National Institute for Health and Clinical Excellence. This same quality metric has been used in other similar meta-analysis of observational studies.²⁵ For quality, scores ranged from 0 (lowest) to 8 (highest) (Table 1). The result of quality assessment for the included studies was as follow: seven studies scored 6, eight studies scored 5, and three studies scored 4.

Quality assessment for cases series.