Bariatric surgery may reduce the overall risk of breast cancer in women with obesity

A systematic review and meta-analysis has indicated that bariatric surgery may reduce the overall risk of breast cancer in women with obesity, according to researchers from China. However, the studies also revealed a paradoxical finding: Despite the overall reduction in risk, the incidence of stage I breast cancer increased in the surgical group. Nevertheless, the study authors acknowledge that as the studies are based on observational data, a causal relationship cannot be confirmed, and the findings of an increased risk of stage I disease should be interpreted with caution.

This systematic review and meta-analysis sought to quantitatively synthesise existing studies to clarify the strength of the association between bariatric surgery and breast  cancer incidence in women. After a literature search and subsequently exclusions, the analysis included a total of 17 studies including 7,129,194 female patients. Of those patients 513,601 underwent bariatric surgery and 6,615,593 were in the control group.

Outcomes

Thirteen studies reported on specific surgical procedures, primarily RYGB, sleeve gastrectomy, and gastric banding, including vertical banded gastroplasty and adjustable gastric banding. Other or unclassified procedures were also included. Three of these studies conducted additional stratified analyses based on surgical type. Three studies conducted subgroup analyses based on menopausal status, but their conclusions were inconsistent. Two of the studies suggested that bariatric surgery could lower the risk of breast cancer in both premenopausal and postmenopausal women. However, the third study found no significant effect.

A total of four studies examined staging information at the time of breast cancer diagnosis in 47,004 patients who underwent bariatric surgery and 171,455 control subjects. All four studies showed no statistically significant difference in breast cancer stage distribution between the surgical and control groups. These four studies provided hormone receptor status data but reached different conclusions. Two of the studies suggested that the incidence of hormone receptor-positive breast cancer was significantly lower in the bariatric surgery group than in the nonsurgical group. The other two studies observed no differences between the groups. Of the 17 included studies, 15 concluded that bariatric surgery reduces the risk of developing breast cancer, while two found no significant association.

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 (oestrogen 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”.

Bariatric surgery primarily reduces the risk of breast cancer by interacting with multiple physiological pathways. The procedure focuses on weight reduction, metabolic improvement, and hormone regulation. It decreases the volume of adipose tissue, the primary site of oestrogen synthesis, lowers oestrogen levels and improves insulin resistance.

“Although evidence suggests that bariatric surgery may reduce the risk of breast cancer in obese women, the clinical applicability of this treatment and which populations would benefit from it are still controversial topics,” the authors noted. “This presents multiple challenges. Addressing these issues is essential to defining the role of bariatric surgery in primary cancer prevention and developing personalised intervention strategies.”

Although bariatric surgery is not currently recommended for cancer prevention, the researchers noted that the results suggest its significant potential as a primary prevention strategy for managing breast cancer risk in women with obesity. Future research should focus on the dose-response relationship between weight loss and risk reduction. Additionally, they stated that researchers should develop precision intervention strategies based on patients’ metabolic characteristics, tumour subtypes, and genetic backgrounds – strategies that would optimise individualised prevention and treatment decisions. They also called for further prospective studies to distinguish between different breast cancer subtypes and investigate the relationship between weight loss and changes in risk.

The findings were reported in the paper, 'Correlation between bariatric surgery and breast cancer risk in women: A systematic review and meta-analysis', published in the World journal of Clinical Oncology. To access this paper, please click here