Surgery-induced weight loss may be associated with lower mortality rates in women with obesity but not men

1. Surgery-induced weight loss was associated with lower cancer incidence and mortality rates in women with obesity, but not men.

Evidence Rating Level: 2 (Good)

Obesity is a risk factor for cancer, and surgery-induced weight loss has been associated with reduced cancer risk and mortality. Although prior studies have found sex differences in surgery-induced weight loss and cancer risk, long-term studies are lacking. This study thus examined the relationship between surgery-induced weight loss and long-term cancer outcomes. This study was a post-hoc analysis of a prospective, controlled intervention trial that recruited patients (37-60 years old) with obesity who underwent bariatric surgery and matched controls who received standard nonsurgical obesity-related care between September 1, 1987, and January 31, 2001, in Sweden. Obesity was defined as body mass index (BMI) ≥34 kg/m2 for men and ≥38 kg/m2 for women. The primary outcomes were cancer events and cancer-related deaths. In total, 2007 patients were in the bariatric surgery group, while 2,040 patients were in the control group. In both groups, about 71% of the group were women. Median follow-up was 26.8 years (interquartile range (IQR) [22.9, 29.6]) in the surgery group and 24.9 years (IQR [18.7, 28.8]) in the control group. Bariatric surgery was associated with a 22% lower overall cancer incidence rate in women (adjusted hazard ratio (HRadj) = 0.78; 95% confidence interval (CI) [0.67, 0.90]), but not in men (sex–treatment interaction p = 0.013). Among women, bariatric surgery was also associated with 22% lower overall cancer mortality rate, although this was borderline statistically significant (HRadj = 0.78 (95% CI [0.61, 1.00]). The associations between surgery and female-specific cancer incidence, as well as female-specific cancer-related mortality, were stronger in women with high baseline insulin levels (insulin-treatment interaction p = 0.021 and 0.039, respectively). Overall, this study found that bariatric surgery was associated with lower cancer incidence and mortality rates in women with obesity, but not men, with stronger associations for female-specific cancers among women with higher baseline insulin levels.

Click here to read this study in PLOS One

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