TOPLINE:
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METHODOLOGY:
- Previous research suggests that bariatric surgery is associated with a lower risk for cancer in people with obesity, as well as female-specific cancers in women with obesity, especially those with higher baseline insulin levels. But there is a need for large prospective studies with more detailed patient information.
- The current secondary analysis included 2867 matched women (mean age, 48 years) from a prospective nonrandomized Swedish trial, which recruited men and women who had obesity between 1987 and 2001.
- Overall, 1420 women underwent bariatric surgery, and 1447 received usual care.
- Median baseline insulin levels were 15.8 μIU/L. In the surgery group, 68.3% of patients had vertical banded gastroplasty, 18.3% underwent gastric banding, and 13.4% underwent gastric bypass.
- The main outcome was breast cancer incidence, as identified from Swedish National Cancer Registry.
TAKEAWAY:
- Over a median follow-up of 23.9 years, 66 breast cancer events occurred in the surgery group and 88 in the usual care group (P = .02).
- Bariatric surgery was associated with a 33% lower risk for breast cancer (adjusted hazard ratio [aHR], 0.67), after excluding cases that occurred within the first 3 years (to account for any undiagnosed breast cancer at baseline) and adjusting for age, body mass index, alcohol, and smoking status.
- Looking at the menopausal status at baseline, bariatric surgery was associated with a reduced risk for breast cancer in premenopausal women (aHR, 0.64) but not postmenopausal women (aHR, 0.84; 95% CI, 0.49-1.45; P = .54).
- Bariatric surgery was also associated with a lower risk for breast cancer in women with baseline insulin levels above the median (aHR, 0.55) than in those with baseline insulin levels below the median (aHR, 1.01).
IN PRACTICE:
“The surgical treatment benefit was predominantly seen in women with hyperinsulinemia, suggesting insulin may be used as a predictor of treatment effect,” the authors wrote. Authors of an accompanying editorial, however, cautioned that “it is not known if insulin levels or insulin resistance are true biomarkers of breast cancer risk in patients with obesity undergoing bariatric surgery” and urged further research into underlying biological mechanisms.
SOURCE:
This study, led by Felipe M. Kristensson, MD, from Institute of Medicine, Department of Molecular and Clinical Medicine, the Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden, was published online in JAMA Surgery. The accompanying editorial was led by Swati A. Kulkarni, MD, of the Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago.
LIMITATIONS:
The study was not randomized. Breast cancer was not a predefined outcome of the main trial. Most patients underwent vertical banded gastroplasty, which is rarely used and could limit applicability of the results; however, vertical banded gastroplasty results in weight loss similar to that observed after sleeve gastrectomy. Follow-up values for insulin and insulin resistance were not available. The researchers noted significant differences in 12 out of 17 baseline characteristics between the two groups, including a larger proportion of postmenopausal women in the usual care group.
DISCLOSURES:
This study was supported by the Swedish state, Swedish Research Council, the Health & Medical Care Committee of the Region Västra Götaland, and the Adlerbert Research Foundation. The authors did not report any conflicts of interest.
A version of this article appeared on Medscape.com.