The association of gallstone disease with risk of colorectal cancer (CRC).
Searches Three electronic databases: PubMed, Web of Science and Scopus will be searched from inception, without any restriction to language. References from retrieved articles will be screened in order to find further relevant studies. For the same reason, we will evaluate in topic systematic reviews and meta-analyses identified during study search.
Types of study to be included Prospective cohort studies
Condition or domain being studied Gallstone disease(GD) is one of the most common ailments of the gastrointestinal tract. Numerous studies have been conducted to ascertain if cholecystectomy is associated with a higher risk of CRC with inconclusive results. To date there hasn’t been a systematic review on the association of symptomatic gallstones or screen-detected gallstones with CRC.
Participants/population We will include studies conducted in adults (aged ≥18 years). Studies conducted exclusively on a group with a baseline chronic disease (e.g. CVD, type 2 diabetes, chronic kidney disease) or pregnant women will be excluded.
Exposure(s) Screen-detected gallstones, symptomatic gallstones or cholecystectomy.
Comparator(s)/control People who do not present with gallstones. Should there be prospective cohort studies without a comparator group we will perform further subgroup analyses.
Main outcome(s) Colorectal cancer diagnosis.
* Measures of effect Relative risks, Odds ratio/ Hazard ratio Additional outcome(s) None
Data extraction (selection and coding) Observational studies will be included in this meta-analysis if they: 1) were prospective in design; 2) reported the exposure of interest as screen-detected gallstones, symptomatic gallstones, gallstone disease or cholecystectomy ; 3) reported the outcome of interest as diagnosis of colorectal cancer; 4) provided odds ratios (OR) and/or relative risks (RR) and the corresponding confidence intervals (CI) or sufficient data to calculate them.
Two authors (G.P. and H.S.) independently will extract data on study characteristics. We will extract the following information from each study: study name, number of exposed, country name or geographical region, the last name of first author, publication year, study period or follow-up time, baseline age, ORs, RRs and 95% CIs for the association between each exposure category and CRC, and covariates. Risk of bias (quality) assessment Begg’s and Egger’s test will be used for publication bias. The Newcastle-Ottawa quality assessment scale will be used for assessing the quality of the studies.
Strategy for data synthesis All study estimates (OR/RR) will be interpreted as relative risk and used as effect size in analyses. They will be calculated using the DerSimonian and Laird random effects models. A two-tailed P value of <0.05 will be considered statistically significant.
Analysis of subgroups or subsets A subgroup analysis by type of exposure, sex, adjustment for covariates, geographical region (US/ Europe/ Asia) and if necessary of studies without comparator groups will be conducted. Contact details for further information
Georgios Polychronidis Harvard T.H. Chan School of Public Health Department of Epidemiology email@example.com Organisational affiliation of the review Harvard T.H. Chan School of Public Health
Review team members and their organisational affiliations Dr Georgios Polychronidis. Heidelberg University Clinic, Study Center of the German Surgical Society & Harvard T.H. Chan School of Public Health
Haziq Siddiqi. Harvard Medical School
Dr. Stefania Papatheodorou.Harvard T.H. Chan School of Public Health
Professor Albert Hofman. Harvard T.H. Chan School of Public Health
Assistant Professor Dr. Mingyang Song. Harvard T.H. Chan School of Public Health & Massachusetts General Hospital
Type and method of review Epidemiologic, Meta-analysis, Systematic review Anticipated or actual start date 01 July 2020 Anticipated completion date 30 January 2021
Funding sources/sponsors Deutsche Forschungsgemeinschaft (DFG) Projektnummer 426308975
Conflicts of interest None
Stage of review
Subject index terms Gallstones; Cholecystectomy; Colorectal cancer