by Ashley Jordan Ferira, PhD, RDN
The latest findings from the landmark Swedish Obese Subjects (SOS) trial demonstrate that bariatric surgery significantly reduces the incidence of female-specific cancers, with the most pronounced cancer risk reductions seen for endometrial cancer and in women with high insulin levels pre-surgery.1-2
The health and economic burdens of obesity in the US, and globally, are immense. Based on the latest 2015-2016 National Health and Nutrition Examination Survey findings from the Centers for Disease Control and Prevention (CDC), the prevalence of obesity in the US is nearly 40% of adults and close to 20% in youth.3 The long-term sequelae of obesity are numerous and deleterious, including advanced cancers and cancer mortality.
Overweight and obesity account for approximately 55% of all US cancer diagnoses in adult women, according to the October 2017 report by the CDC.4 While the rates of non-obesity related cancers declined by 13% from 2005 to 2014, the rates of obesity-related cancers increased by seven percent.4 Effective obesity interventions that induce significant, long-term weight loss are crucial to reduce obesity-related comorbidities.
Bariatric surgery is not only associated with long-term weight loss but also leads to reductions in incidence of diabetes, stroke, myocardial infarction (MI), atrial fibrillation (AF), and overall mortality.5-6 The latest SOS trial report by Anveden and colleagues was recently published in Gynecologic Oncology.1 The large, prospective controlled study consisted of 1,420 women from the SOS cohort who received bariatric surgery (18.3% gastric banding; 68.3% vertical banded gastroplasty; 13.4% gastric bypass) and 1,447 matched control participants who received conventional obesity treatment. At baseline, the women’s age spanned 37-60 years, with an average body mass index ≥ 38 kg/m2. Median follow-up duration was 18.1 years. Cancer events were obtained from the Swedish National Cancer Registry.
At two years post-surgery, SOS women lost 61.6 pounds, with an average 46.2 pound weight loss maintained at 10- and 15-year follow-up visits. In contrast, weight changes in the control group were minimal. Approximately half (49%) of all observed first-time cancers during the study follow-up period were female-specific, defined as breast, endometrial, ovarian, and all other gynecological cancers.
Compared to usual care, bariatric surgery significantly:
– Reduced the risk of overall cancer by 29%
– Reduced the risk of female-specific cancers by 32%
– Reduced the risk of endometrial cancer by 44%
– (No significant risk reduction was observed for cervical cancer)
Interestingly, a greater treatment benefit from bariatric surgery was observed in patients with high baseline insulin levels vs. those with low insulin levels.1 This finding is noteworthy, since hyperinsulinemia may play a causal role between obesity and cancer pathogenesis.7
The SOS trial clearly demonstrates a reduction in overall cancer and female-specific cancer incidence in women.1 Future research is needed to clarify whether bariatric surgery mitigates oncologic mortality and improves oncologic quality of life. For individual patients, HCPs should weigh the potential benefits (i.e. significant, long-term weight loss and reduced risk of many serious diseases) and risks (e.g. surgical morbidity, prolonged metabolic derangements, increased hospitalizations, increased inpatient and outpatient resource utilization) of bariatric surgery for the treatment of obesity and comorbid conditions.
Why is this Clinically Relevant?
- The obesity epidemic now impacts approximately 40% and 20% of US adults and youth, respectively3
- Effective interventions with long-term success are needed to reduce obesity prevalence and its associated comorbidities, including obesity-related cancers
- Findings from the landmark, prospective SOS trial demonstrate that bariatric surgery reduces the incidence of overall cancer in women by 29% and also lowers the risk of female-specific cancers by 32%, with a 44% risk reduction for endometrial cancer1
- The treatment benefit of bariatric surgery in the SOS trial was greatest in women with hyperinsulinemia pre-surgery1
- For individual patients, HCPs should weigh the risks and benefits of bariatric surgery for the treatment of obesity and comorbid conditions
- Anveden A, Taube M, Peltonen M, et al. Long-term incidence of female-specific cancer after bariatric surgery or usual care in the Swedish Obese Subjects Study. Gynecol Oncol. 2017;145(2):224-229.
- Medscape. Bariatric surgery reduces female-specific cancers. https://www.medscape.com/viewarticle/880722. Updated May 29, 2017. Accessed September 29, 2017.
- Hales CM, Carroll MD, Fryar CD, Ogden CL. Prevalence of obesity among adults and youth: United States, 2015–2016. NCHS data brief, no 288. Hyattsville, MD: National Center for Health Statistics. 2017.
- CDC. Cancers associated with overweight and obesity make up 40 percent of cancers diagnosed in the United States. https://www.cdc.gov/media/releases/2017/p1003-vs-cancer-obesity.html. Accessed October 17, 2017.
- Sjostrom L. Review of the key results from the Swedish Obese Subjects (SOS) trial – a prospective controlled intervention study of bariatric surgery. J Intern Med. 2013; 273(3):219-234.
- Jamaly S, Carlsson L. Bariatric surgery and the risk of new-onset atrial fibrillation in Swedish Obese Subjects. J Am Coll Cardiol. 2016;68(23):2497-2504.
- Grote VA, Becker S. Diabetes mellitus type 2 – an independent risk factor for cancer? Exp Clin Endocrinol Diabetes. 2010;118(1):4-8.