Correlation between bariatric surgery and breast cancer risk in women: A systematic review and meta-analysis

Table 1 Characteristics of the studies included in the meta-analysis

Ref.	Country of origin	Study design	Time period	Follow-up period	Sample size	Female (%)	Mean age (years), mean ± SD	BMI (kg/m2)	Breast cancer risk, n (%)	Type of bariatric surgery (%)	Main findings	HR (95%CI)
				Surgery	Surgery	Surgery	Surgery	Surgery	Surgery
				Control	Control	Control	Control	Control	Control
Wei et al[22], 2021	Hong Kong SAR, China	Retrospective cohort study	2006-2017	37 months	345	174 (50.4)	51.0 ± 11.0	37.5 ± 4.8	2 (0.011)1	SG: 83.2, RYGB: 14.2, AGB: 2.6	Bariatric surgery does not significantly impact the incidence of breast cancer	0.394 (0.048-1.424)
					1599	787 (49.2)	51.7 ± 12.8	36.9 ± 6.3	13 (0.017)1			0.521 (0.277-0.891)
Chittajallu et al[27], 2023	United States	Retrospective cohort study	2002-2022	10 years	557892	44073 (79.0)	43.1 ± 14.1	> 35	501 (0.9)	NA	The incidence rate of new breast cancer cases was significantly lower among obese adults who had undergone bariatric surgery compared to those who had not	0.753 (0.678-0.836)
					557892	43990 (78.9)	44.6 ± 15.3		751 (13.5)
Doumouras et al[28], 2022	Canada	Retrospective population-based, matched cohort study	From January 2010 to December 2016	9 years	12724	12724 (100.0)	45.09 ± 0.98	> 35	99 (0.79)3	NA	Bariatric surgery is associated with a reduced incidence of breast cancer and lower tumor grade in obese women	0.81 (0.69-0.95)
					12724	12724 (100.0)	45.02 ± 1.08		133 (1.09)3
Feigelson et al[24], 2020	United States	Retrospective cohort study	From January 1, 2005 to December 31, 2012	47.5 ± 23.2 months	17998	17998 (100.0)	44.6 ± 11.1	44.6 ± 6.6	Premenopausal 65	SG: 27.0, RYGB: 61.3, AGB: 5.6	Bariatric surgery is associated with a reduced risk of breast cancer in both premenopausal and postmenopausal women	Premenopausal 072 (0.54-0.94)
									Postmenopausal 68			Postmenopausal 055 (0.42-0.72)
				40.8 ± 24.7 months	53889	53889 (100.0)	44.7 ± 11.0	44.1 ± 6.2	Premenopausal 236			Overall 063 (0.52-0.76)
									postmenopausal 331
Christou et al[29], 2008	Canada	Observational cohort study	From January 1986 to June 2002	5 years	1035	679 (65.6)	45.1 ± 11.6	NA	12 (1.16)	RYGB: 81.3, VGB: 18.7	Patients in the bariatric surgery group had a lower incidence of breast cancer than those in the control group	0.17 (0.098-0.311)
					5746	3678 (64.0)	46.7 ± 13.1	NA	362 (6.31)
Tome et al[21], 2025	Israel	Retrospective cohort study	2012-2020	NA	696	696 (100.0)	60.7 ± 10.0	32.4 ± 6.5	29 (4.17)	NA	Bariatric surgery is associated with a reduced overall incidence of breast cancer	NA
					1164	116 (100.0)	61.0 ± 10.1	38.6 ± 4.1	14 (12.10)
Kristensson et al[26], 2024	Sweden	Prospective, matched, intervention study	From September 1, 1987, to January 31, 2001	23.9 years (20.1-27.1)	1420	1420 (100.0)	47.2 ± 6.0	42.8 ± 4.3	66 (4.65)	AGB: 18.3, RYGB: 68.3, VGB: 13.4	The bariatric surgery group showed a significantly reduced risk of breast cancer compared with the conventional treatment group	0.68 (0.49-0.94)
					1447	1447 (100.0)	48.8 ± 6.3	40.7 ± 4.6	88 (3.32)
Adams et al[30], 2009	United States	Retrospective cohort study	1984-2002	12.3 ± 5.7 years	6596	5654 (85.7)	38.9 ± 10.3	44.9 ± 7.6	Premenopausal 49	RYGB: 100.0	Gastric bypass surgery may reduce the overall incidence of cancer, but it does not affect breast cancer cases in premenopausal or postmenopausal women	Premenopausal 093 (0.63-1.37)
									Postmenopausal 24			Postmenopausal 096 (0.57-1.63)
				11.8 ± 5.6 years	9442	7872 (83.4)	39.1 ± 10.7	47.4 ± 6.5	Premenopausal 65			Overall 091 (0.67-1.24)
									Postmenopausal 40
Tao et al[31], 2020	Denmark, Finland, Iceland, Norway, and Sweden	Retrospective cohort study	From January 1, 1980 to December 31, 2012	33 years5	49096	36533 (74.5)	≥ 18	NA	179 (0.36)6	RYGB: 72.4, restrictive: 220, other: 5.6	Women experience a reduced risk of breast cancer after bariatric surgery	0.81 (0.69-0.95)
					472067	318,596 (67.5)		NA	3328 (0.70)7
Desai et al[32], 2022	United States	Retrospective cohort study	1999-2014	NA	279171	215078 (77.04)	43.9 ± 25.2	NA	95 (0.04)	NA	Patients with morbid obesity who undergo bariatric surgery have a significantly lower risk of developing breast cancer	0.07 (0.06-0.09)
				NA	7393337	4758352 (64.36)	54.9 ± 36.4	NA	35181 (0.74)
Adams et al[18], 2023	United States	Retrospective cohort study	1982-2019	38 years5	21837	17271 (100.0)	42.2 ± 11.7	46.0 ± 8.3	Premenopausal 123	AGB: 11.8, RYGB: 71.1, duodenal switch: 3.9, SG: 13.1	Women who underwent bariatric surgery were significantly less likely to develop breast cancer than those who did not, including both pre- and postmenopausal cases	Premenopausal 072 (0.54-0.95)
									Postmenopausal 249			Postmenopausal 0.79 (0.64-0.97)
					21837	17271 (100.0)	42.3 ± 11.9	46.2 ± 6.8	Premenopausal 157			NA
									Postmenopausal 302
Mackenzie et al[33], 2018	United Kingdom	Retrospective population-based, matched cohort study	1997-2012	55 (30-94) months7	8794	7069 (80.4)	42.0 (35.0-50.0)7	NA	61 (0.86)	RYGB: 56.6, VGB: 33.6, SG: 9.8	Patients who underwent bariatric surgery had a reduced risk of developing breast cancer compared to those who did not undergo the surgery	0.25 (0.19-0.33)
					8794	7069 (80.4)	42.0 (35.0-50.0)7	NA	239 (3.38)
Aravani et al[34], 2018	United Kingdom	Retrospective population-based, matched cohort study	1997-2013	3.0 (range 1-16) years	39474	30436 (76.6)	44.8	NA	101 (0.33)	Restrictive: 520, other: 48.0	Bariatric surgery and subsequent weight loss are associated with a reduced risk of developing breast cancer	SIR, 0.76 (0.62-0.92)
				2.5 (range 1-16) years	962860	606005 (62.9)	53.1	NA	3086 (0.51)			SIR 1.08 (1.04-1.11)
Hassinger et al[35], 2019	United States	Retrospective propensity-matched cohort study	1985-2015	6.0 (2.6-10.8)7	24302	2430b (100.0)	42.0 (35.0-51.0)7	48.0 (43.0-53.0)7	17 (0.70)	GB: 11.9, RYGB: 79.4, SG: 7.5, other 1.2	The rate of breast cancer of any type among female patients who underwent bariatric surgery was lower than that observed among propensity-matched controls	NA
				5.0 (3.6-10.3)7	24302	2430b (100.0)	42.0 (31.0-53.0)7	47.1 (40.6-55.5)7	32 (1.31)
Doumouras et al[36], 2023	Canada	Retrospective matched cohort study	From January 1, 2010 to December 31, 2016	5 years	13852	13852 (100.0)	45.1 ± 10.8	NA	103 (0.74)	NA	Bariatric surgery is associated with a reduced risk of breast cancer in obese women, bringing their risk level comparable to that of women with a BMI below 25	1.40 (1.18-1.57)3
				5 years	55408	55408 (100.0)	45.1 ± 10.9	NA	556 (1.00)
Stenberg et al[19], 2025	Sweden	Retrospective matched cohort study	From January 1, 2007 to December 31, 2020	7.7 ± 3.39 years	68424	51733 (75.7)	40.5 ± 11.13	41.8 ± 5.62	60 (0.12)	RYGB: 80.90, SG: 19.10	The overall cancer incidence risk after bariatric surgery has approached that of the general population, and the risk of breast cancer has decreased	IRR 0.78 (0.71-0.86)
				7.8 ± 3.39 years	640944	478857 (74.7)	40.1 ± 11.07	NA	707 (0.15)
Tsui et al[37], 2021	United States	Retrospective matched cohort study	2006-2012	10 years	55781	55781 (100.0)	NA	NA	834 (1.50)	GB: 26.79, RYGB: 43.98, SG: 11.33, other 18.06	Patients who underwent bariatric surgery had a lower incidence of breast cancer compared with obese patients who did not undergo the procedure	NA
					247102	247102 (100.0)	NA	NA	4313 (1.75)

¹Breast and genital organs.

²After matching.

³After a 1-year lag period.

⁴All patients underwent surgery for breast cancer.

⁵The longest follow-up period.

⁶Includes male patients.

⁷Listed as median (interquartile range).

HR: Hazard ratio; CI: Confidence interval; SG: Sleeve gastrectomy; RYGB: Roux-en-Y gastric bypass; AGB: Adjustable gastric band; NA: Not available; VBG: Vertical banded gastroplasty; GB: Gastric banding; SIR: Standardized incidence ratio; IRR: Incidence rate ratio; BMI: Body mass index.

Table 2 Characteristics of breast cancer in surgical and non-surgical groups, n (%)

Ref.	Arm	Incident breast cancer	Stage at diagnosis	ER+ breast cancer	PR+ breast cancer	HER2+ breast cancer
Doumouras et al[28], 2022	Surgery	99 (0.79)1	Stage 1: 59 (66.3)	ER+: 47 (64.8)	PR+: 43 (59.1)	HER2+: 6 (8.0)
			Stage 2: 24 (27)	ER-: 6 (9.1)	PR-: 10 (14.8)	HER2-: 46 (63.6)
			Stage 3 and 4: 6 (6.7)	Unknown: 22 (26.1)	Unknown: 22 (26.1)	Unknown: 23 (28.4)
	Control	133 (1.09)1	Stage 1: 69 (60.5)	ER+: 54 (61.8)	PR+: 47 (54.5)	HER2+: 12 (12.2)
			Stage 2: 35 (30.7)	ER-: 7 (8.1)	PR-: 14 (15.4)	HER2-: 44 (51.2)
			Stage 3 and 4: 10 (8.8)	Unknown: 35 (30.1)	Unknown: 35 (30.1)	Unknown: 40 (36.6)
	P value		0.423	0.045	0.041	0.012
Feigelson et al[24], 2020	Surgery	133 (0.7)	Stage 0: 32 (24.1)	ER+: 111 (83.5)	PR+: 98 (73.7)
			Stage 1: 58 (43.6)	ER-: 19 (14.3)	PR-: 19 (14.3)
			Stage 2: 36 (27.1)	Unknown: 3 (2.2)	Unknown: 16 (12.0)
			Stage 3 and 4: 7 (5.3)
	Control	567 (1.1)	Stage 0: 120 (21.2)	ER+: 453 (79.9)	PR+: 380 (67.0)
			Stage 1: 211 (37.2)	ER-: 91 (16.0)	PR-: 89 (15.7)
			Stage 2: 164 (28.9)	Unknown: 23 (4.1)	Unknown: 98 (17.3)
			Stage 3 and 4: 67 (11.8)
	P value		0.20	0.60	0.60
Hassinger et al[35], 2019	Surgery	17 (0.7)	Stage 0: 2/11 (18.2)	ER+: 4/11 (36.4)	PR+: 5/11 (45.5)	HER2+: 3/11 (27.3)
			Stage 1: 7/11 (63.6)	ER-: 7/11 (63.6)	PR-: 6/11 (54.5)	HER2-: 8/11 (72.7)
			Stage 2: 2/11 (18.2)
			Stage 3 and 4: 0 (0)
	Control	32 (1.3)	Stage 0: 7/29 (24.1)	ER+: 22/31 (71.0)	PR+: 22/31 (71.0)	HER2+: 2/31 (6.5)
			Stage 1: 12/29 (41.4)	ER-: 9/31 (29.0)	PR-: 9/31 (29.0)	HER2-: 29/31 (93.5)
			Stage 2: 7/29 (24.1)
			Stage 3 and 4: 3/29 (10.4)
	P value		0.53	0.04	0.13	0.07
Doumouras et al[36], 2023	Surgery	103 (0.74)	Stage 1: 273 (55.4)	ER+: 48/76 (63.2)	PR+: 43/76 (56.6)	HER2+: 6/76 (7.9)
			Stage 2: 156 (31.6)	ER-: 5/76 (6.5)	PR-: 10/76 (13.2)	HER2-: 46/76 (60.5)
			Stage 3 and 4: 64 (13.0)	Unknown: 23/76 (30.3)	Unknown: 23 (30.3)	Unknown: 24/76 (31.6)
	Control	556 (1.00)	Stage 1: 60 (67.4)	ER+: 232/406 (57.1)	PR+: 207/406 (51.0)	HER2+: 52/406 (12.8)
			Stage 2: 24 (27.0)	ER-: 48/406 (11.8)	PR-: 73/406 (18.0)	HER2-: 221/406 (54.4)
			Stage 3 and 4: 5 (5.6)	Unknown: 126/406 (31.0)	Unknown: 126/406 (31.0)	Unknown: 133/406 (32.8)
	P value	0.29	0.94	0.9	0.65

¹After a 1-year lag period.

Descriptive tumor characteristics are not available for all breast cancer patients. ER: Estrogen receptor; PR: Progesterone receptor; HER2: Human epidermal growth factor receptor 2.