Step 3. Search, selection, data abstraction and synthesis
All questions selected by the GSG and GDG were converted into a specific question format using the PICO (patient, intervention, comparison and outcome) model. Selection criteria for each question were determineda priori based on the patient population and exposures in each question. Only comparative studies (systematic reviews of comparative studies, randomized controlled trials, cohort studies, case-control studies, and cross-sectional studies) were eligible for inclusion. A systematic search of PubMed through February 1, 2024, was performed to find studies addressing the questions included in the CPG. Additionally, we manually reviewed the reference lists of all relevant systematic reviews and included studies to find additional eligible studies. The titles and abstracts of all identified references were reviewed by a clinician and a methodologist from the GSG. Studies identified for full-text review were then reviewed by all members of the GSG, and any reasons for exclusion were noted.
Data from the included studies were extracted by two members of the GSG. The risk of bias in the included studies was assessed using the appropriate tool for each study design. The Cochrane RCT tool was used for randomized controlled trials. The Newcastle-Ottawa tool was used for cohort and case-control studies. Data on outcomes from similar studies were extracted and pooled when appropriate by using the random-effects model. The main outcomes of interest were overall survival, mortality, completeness of resection, local recurrence, complications, and intensity of therapy, as important outcomes to inform recommendations. All comparative analyses were performed using the RevMan software package. Pooled estimated for each outcome and certainty of evidence were summarized using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) Summary of Findings tables.