Published online Mar 24, 2026. doi: 10.5306/wjco.v17.i3.114774
Revised: November 30, 2025
Accepted: February 2, 2026
Published online: March 24, 2026
Processing time: 176 Days and 18.8 Hours
Obesity is a significant global public health challenge and a key risk factor for several types of cancer. Breast cancer, the most common malignant tumor among women, is strongly associated with obesity. Currently, bariatric surgery is the most effective approach for long-term weight management and improving metabolic health. Although research indicates that bariatric surgery decreases the likelihood of developing certain cancers, its impact on breast cancer incidence is unclear.
To investigate the relationship between bariatric surgery and breast cancer risk in women.
We conducted a comprehensive search of multiple electronic databases for original studies comparing the incidence of breast cancer in women who underwent bariatric surgery to that in a control group. For the meta-analysis, we used a random-effects model and performed stratified analyses based on variables such as menopausal status, tumor stage, and hormone receptor status to examine effect modification. We evaluated the rigor of the study methods using the Risk of Bias in Non-randomized Studies of Interventions tool. We quantified heterogeneity using the I2 statistic and assessed the quality of the evidence using the Grading of Recommendations, Assessment, Development and Evaluation approach. Additionally, we created a funnel plot and performed a Begg’s test to evaluate publication bias.
A total of 17 observational studies, including 7129194 female patients, were included in the analysis. Of those patients, 513601 underwent bariatric surgery, and 6615593 were in the control group. A meta-analysis revealed that bariatric surgery is significantly associated with a reduced overall risk of breast cancer [relative risk (RR) = 0.52; 95% confidence interval (CI): 0.38-0.71; P < 0.00001]. However, substantial heterogeneity was observed (I2 = 98%). Subgroup analysis showed a consistent reduction in risk among premenopausal (RR = 0.84; 95%CI: 0.72-0.99; P = 0.04) and postmenopausal (RR = 0.75; 95%CI: 0.60-0.92; P = 0.006) women. Analysis by disease stage revealed an 18% increase in the RR of stage I cancer in the surgery group (RR = 1.18; 95%CI: 1.06-1.32; P = 0.003). Conversely, the incidence of stage III-IV cancer decreased significantly (RR = 0.50; 95%CI: 0.31-0.82; P = 0.006). The incidence of stage II cancer did not change significantly (RR = 0.89; 95%CI: 0.73-1.10; P = 0.28). No significant association was observed for hormone receptor-positive (estrogen receptor-positive, progesterone receptor-positive, and human epidermal growth factor receptor 2+) subtypes. The overall risk of bias was moderate to high. Based on the Grading of Recommendations, Assessment, Development and Evaluation criteria and other considerations, the quality of the evidence was ultimately rated as “moderate”.
According to observational data, bariatric surgery appears to reduce the overall risk of breast cancer, especially among postmenopausal women. However, the observed association with an increased risk of stage I cancer should be interpreted with caution. Further prospective studies are needed to establish causality.
Core Tip: Obesity is a well-established risk factor for breast cancer. Although bariatric surgery is an effective intervention for long-term weight management and metabolic improvement, its impact on breast cancer incidence remains unclear. Our systematic review and meta-analysis of 17 observational studies indicates that bariatric surgery is associated with an overall reduced risk of breast cancer in obese women. This protective effect was observed in both premenopausal and postmenopausal women, though it was more pronounced in the latter group. However, the observational design precludes establishing causality. An observed increased risk of stage I cancer requires cautious interpretation. These findings offer a new per