Researchers at the University of North Carolina, Lineberger Comprehensive Cancer Center reported that surgical weight loss was able to inhibit breast tumor growth, while similar weight loss through diet was not. Researchers hope that the findings, seen in a mouse model of breast cancer, will help them to better understand the surgery’s metabolic effect on tumors and replicate those protective effects in cancer patients.
Study results will be delivered on April 18 at the 2016 American Association of Cancer Research Annual Meeting in New Orleans, in a presentation titled “Surgical weight loss via sleeve gastrectomy, but not a low-fat diet, reverses the pro-tumorigenic effects of obesity.”
Basal-like breast cancer (BLBC) is a subtype of breast cancer, characterized by the absence of estrogen receptors, progesterone receptors, and HER-2 overexpression. As such, several hormonal and HER-2 specific treatments are ineffective for these cancers, which tend to be more aggressive and lethal than other subtypes.
Obesity has been shown to be a risk factor for several types of breast cancer, and is associated with an increased incidence of BLBC. Although data can be conflicting, previous research suggests that only interventions that result in significant sustained weight loss, such as bariatric surgery, are effective in producing anti-cancer effects.
Researchers set out to confirm if surgery was indeed more effective in preventing or controlling BLBC compared to similar weight loss achieved through diet. The team analyzed mice that were fed a low-fat diet and a high-fat diet, resulting in one group of normal weight mice and another of chronic obese mice. Obese mice were then randomized to either a surgical weight loss intervention (sleeve gastrectomy) a dietary weight loss intervention, or a subgroup left untreated. After weight stabilization, all the mice were injected with mammary tumor cells in order to model BLBC.
Tumor growth in the obese mice that underwent surgery was found to be equivalent to those mice kept at normal weight, while mice that had lost equal weight and body fat through diet had fewer anti-cancer benefits, with tumor growth similar to that seen in the untreated obese mice.
Moreover, mice that underwent surgery had lower levels of insulin and inflammatory proteins, both associated with molecular advancement of cancer, suggesting that surgery decreases the obesity-linked drivers of breast cancer growth.
“We are not going to solve this growing problem through bariatric surgery, which, despite being effective, is too expensive and too difficult to be done on everyone who is obese. Our goal is to understand what the surgery is doing metabolically to slow tumors, and replicate those protective effects through combinations of diet, exercise and possibly drugs that target some of the same pathways as the bariatric surgery,” Professor Stephen Hursting, the study’s senior author, said in a news release.