Cholecystectomy and the risk of alimentary tract cancers: A systematic review

Table 2 Descriptive characteristics of studies on the association between cholecystectomy and oesophageal squamous cell cancer

Ref.	Period of study	Study design	No. of cases	No. of controls	Exposure ascertainment	Outcome ascertainment	Follow-up (yr)	Effect estimate	Adjustments	Quality of publication
Freedman et al[20], 2000	1994-1997	Case-control	167	820	Self-report	Pathology records		OR = 0.82 (0.43-1.54)	Age, gender, alcohol, smoking, BMI, physical activity, education, diet	37
Nogueira et al[21], 2014	1992-2005	Case-control	100/4732	2572/100000	Medicare database	Cancer registry	> 6	OR = 0.85 (0.69-1.04)	Age, gender, diabetes	49
Ichimiya et al[26], 1986	1953-1984	Cohort	29	1238	Self report	Death registry	< 31	0.59 (0.26-1.36	Age, gender	48
Freedman et al[23], 2001	1965-1997	Cohort	129/268312	NA	National registry	Cancer registry	> 10	SIR = 0.9 (0.7-1.1)	Age, gender	38
Lagergren and Mattsson[24], 2011	1965-2008	Cohort	193/345251		NA	Cancer registry	15	SIR 0.93 (0.81-1.08)	Age, gender, calendar year	40

Ichimiya et al[26], 1986, reported on oesophageal cancer without specifying pathology of cancer. NA: Not available; BMI: Body mass index.