Association between tobacco exposure and bladder cancer recurrence: A systematic review and meta-analysis

Table 1 Characteristics of the included studies

Ref.	Area	Sort	Period	Mean follow-up time (months)	Sample size	Disease stage	NOS score	Cur:For:Non
Michalek et al[14], 1985	United States	Retrospective	1963-1975	N/A	354	NMIBC	7	132:128:94
Grotenhuis et al[16], 2015	Netherlands	Forward-looking	2007-2012	12	963	NMIBC	8	292:490:181
Wyszynski et al[25], 2014	Lebanon	Forward-looking	1994-2002	37	857	NMIBC	8	214:379:123
Chen et al[19], 2007	Taiwan	Retrospective	1997-2005	N/A	206	NMIBC	6	78:64:64
Leibovici et al[20], 2005	United States	Forward-looking	1995-2003	15	519	NMIBC	7	185:239:95
Yuruk et al[26], 2017	Turkey	Forward-looking	2013-2014	32	187	NMIBC	9	114:35:38
van Osch et al[24], 2018	United Kingdom	Forward-looking	2005-2011	51	722	NMIBC	8	336:283:103
Ogihara et al[12], 2015	Japan	Retrospective	1995-2012	N/A	634	NMIBC	8	181:154:299
Rava et al[21], 2018	Spain	Forward-looking	1998-2001	N/A	936	MIBC	7	401:369:166
Hagiwara et al[11], 2013	Japan	Retrospective	1994-2010	N/A	245	NMIBC	7	72:52:121
Serretta et al[22], 2013	Italy	Retrospective	2002-2003	48	395	NMIBC	7	127:171:97
Serretta et al[23], 2020	Italy	Forward-looking	2008-2012	N/A	194	NMIBC	7	67:127

NMIBC: Non-muscle- invasive bladder cancer; MIBC: Muscle-invasive bladder cancer; NOS score: Newcastle-Ottawa scale.

Table 2 Assessment of quality of studies by the Newcastle–Ottawa scale

Ref.	Selection			Comparability			Outcome			Score
	1	2	3	4	5a	5b	6	7	8
Michalek et al[14], 1985	1	1	1	1	1		1	1		7
Grotenhuis et al[16], 2015	1	1	1	1	1	1	1	1		8
Wyszynski et al[25], 2014	1	1	1	1	1		1	1	1	8
Chen et al[19], 2007	1		1	1	1	1	1			6
Leibovici et al[20], 2005	1	1	1	1			1	1	1	7
Yuruk et al[26], 2017	1	1	1	1	1	1	1	1	1	9
van Osch et al[24], 2018	1	1	1		1	1	1	1	1	8
Ogihara et al[12], 2015	1	1		1	1	1	1	1	1	8
Rava et al[21], 2018	1		1	1	1	1	1	1		7
Hagiwara et al[11], 2013	1		1		1	1	1	1	1	7
Serretta et al[22], 2013	1		1	1	1		1	1	1	7
Serretta et al[23], 2020	1	1	1	1	1	1			1	7

1 = the exposed cohort is representative; 2 = Study cohort with unexposed; 3 = Exposure factor identified; 4 = No positive results at the start of the study; 5 = Cohort comparability based on design or analysis [(a) Study age controls; (b) Study controls for any additional factors); 6 = Outcome assessment is reliable; 7 = Follow-up time is long enough; 8 = Adequacy of cohort follow-up.

Table 3 Summary of meta-analysis results on smoking status and disease recurrence in patients with bladder cancer

Analysis specification	n	Tobacco exposure vs never smoking		Current smoker vs never smoker		Former smoker vs never smoker		Current smoker vs former smoker
		OR (95%CI)	I2 (%)	OR (95%CI)	I2 (%)	OR (95%CI)	I2 (%)	OR (95%CI)	I2 (%)
All	12	1.84 (1.15-2.93)	91	1.85 (1.11-3.07)	91	1.73 (1.09-2.73)	88	1.01 (0.74-1.38)	83
Race			91		90		88		83
Caucasian	7	1.33 (1.12-1.58)		1.32 (1.09-1.59)		1.29 (1.07-1.56)		1.03 (0.89-1.18)
Noncaucasian	5	2.13 (1.74-2.61)		2.24 (1.78-2.83)		1.76 (1.39-2.23)		1.16 (0.93-1.45)
Study design			91		91		88		83
Multi	6	1.98 (1.68-2.32)		2.07 (1.73-2.48)		1.67 (1.39-2.01)		1.21 (1.04-1.40)
Single	5	1.09 (0.87-1.37)		1.00 (0.78-1.30)		1.12 (0.87-1.43)		0.81 (0.65-1.00)
Sort			91				88		84
Retrospective	5	3.23 (2.59-4.02)		3.23 (2.52-4.14)		3.15 (2.44-4.08)		1.04 (0.83-1.32)
Forward	6	1.05 (0.89-1.24)		1.09 (0.91-1.32)		0.97 (0.81-1.17)		1.10 (0.95-1.28)
Disease stage			91		91		88		83
NMBIC	10	1.93 (1.65-2.26)		1.83 (1.54-2.18)		1.81 (1.52-2.15)		0.94 (0.81-1.09)
Others	2	1.00 (0.78-1.29)		1.20 (0.91-1.59)		0.85 (0.65-1.12)		1.38 (1.11-1.72)
Research cycle			91		91		88		83
End of before 2010	5	1.26 (1.01-1.56)		1.22 (0.95-1.56)		1.25 (0.99-1.59)		0.93 (0.76-1.14)
End after 2010	7	1.88 (1.59-2.21)		1.92 (1.60-2.31)		1.59 (1.32-1.92)		1.14 (0.98-1.33)

OR: Odd ratios; I²: I-squared statistic; NMBIC: Non-muscle- invasive bladder cancer.