Table 3.

Quality assessment and risk of bias of included studies

Author, year	Population-based cohort	Ascertainment of outcome (tumor stage)	Detailed information on ascertainment of outcome (survival)	Reported length of follow-up time	Analyses controlled for prognostic factors (e.g., tumor stage, treatment, liver function)	Adjusted for socioeconomic and/or geographic factors
Davila, 2006	Yes	Yes	Yes	No	Yes**	No
Kemmer, 2008	No	Yes	No	No	No	No
Cubillas § , 2009	No	Yes	No	No	No	No
Ochner, 2010	No	No	Yes	No	Yes	No
Yu, 2010	No	Yes	Yes	No	Yes*	Yes*
Zaydfudim, 2010	Yes	No	Yes	No	Yes	Yes**
Jan, 2012	No	No	No	No	Yes*	Yes*
Aparo, 2014	No	Yes	Yes	No	Yes**	No
Al-Rajabi, 2015	No	Yes	No	No	No	No
Hoehn, 2015	Yes	Yes	No	Yes	Yes*	No
Aru § , 2016	No	No	No	No	No	No
Chan § , 2016	No	No	No	No	No	No
Stewart, 2016	Yes	Yes	Yes	No	Yes**	Yes**
Alkhalili, 2017	No	Yes	Yes	No	No	No
Chayanupatkul, 2017	Yes	No	Yes	Yes	Yes*	No
Mokdad, 2017	Yes	No	Yes	No	Yes**	Yes*
Venepalli, 2017	No	Yes	Yes	Yes	No	No
Franco, 2018	Yes	Yes	Yes	Yes	Yes**	No
Gabriel, 2018	Yes	No	No	Yes	No	No
Atiemo, 2019	Yes	No	Yes	No	No	No
Dakhoul, 2019	No	Yes	Yes	No	No	No
Estevez, 2019	No	Yes	Yes	Yes	Yes**	Yes*
Jones, 2018	No	Yes	Yes	No	Yes**	Yes*
Kim, 2018	No	No	Yes	Yes	Yes*	No
Sobotka, 2018	Yes	No	No	No	Yes*	Yes*
Jones, 2019	Yes	Yes	Yes	Yes	Yes**	Yes*
Kuftinec, 2019	No	Yes	No	No	No	No
Rich, 2019	No	Yes	Yes	Yes	Yes**	Yes*
Yang § , 2019	Yes	No	No	No	Yes	Yes**
Zhang, 2019	No	No	Yes	Yes	No	No
Brar, 2020	Yes	No	Yes	No	Yes**	No
Kangas-Dick, 2020	Yes	No	No	No	Yes	Yes*
Lee, 2020	No	No	Yes	Yes	Yes**	Yes*
Pomenti, 2020	No	Yes	Yes	No	Yes**	No
Scaglione, 2020	No	Yes	Yes	No	Yes*	Yes*

^*One asterisk denotes study adjusted for either tumor stage or treatment; two asterisks denotes study adjusted for both tumor stage and treatment

^§denotes abstract only