The news release provides a good summary of the methods behind the study, the benefits found, and where the findings fit in the larger issue of how weight contributes to poor health. It could have been improved with an exploration of costs and the potential harms from bariatric surgery. In addition, it’s not clear that the reported results (e.g. resolution of precancerous changes in a small number of women) amounts to a “dramatic benefit” for “preventing cancer” as the headline suggests. The release would have done well to more carefully frame these cancer-related effects, which are of uncertain importance.
According to the National Cancer Institute, obesity is associated with increased risk of many cancer types: esophageal, pancreatic, colorectal, breast, endometrial, kidney, thyroid, and gallbladder. In 2007, a study using NCI Surveillance, Epidemiology, and End Results (SEER) data, estimated that “in the United States, about 34,000 new cases of cancer in men (4 percent) and 50,500 in women (7 percent) were due to obesity” (2015). Their prediction model estimated that continuation of existing trends in obesity will lead to about 500,000 additional cases of cancer in the United States by 2030. This topic is important because, if there were a way to reduce the risk of cancer by means of bariatric surgery, the overall burden of disease in the US would be reduced.
There is no mention of costs in the release (or in the study).
This release does something wonderful. It sums up the main findings from the study – including a quantification of some benefits – at the very top of the release. What would have made the quantification even better would have been breaking down the raw numbers. How many women lost how much weight? Not just the averages. And when the release talks about improvements in other outcomes such as physical quality of life and insulin levels, what sort of changes are we talking about? Were they just statistically significant or would they really be meaningful to these patients in their daily lives?
Another area of concern is the headline, which suggests that bariatric surgery offers “dramatic benefits” for “preventing cancer.” This seems to be referring to a reduction in precancerous changes in a small number of women and some changes in these women’s gut bacteria. We would be hard-pressed to characterize those changes as a “dramatic” cancer-prevention benefit. In fact, the study offered no proof that the surgery prevented any cancers at all. We’ll address this issue down below under “Unjustifiable Language.”
There is no mention of harms or risks in the release. Bariatric surgery has many well-documented short- and longer-term risks. According to the Mayo Clinic, risks associated with the procedure may include excessive bleeding, infection, blood clots, and leaks in the gastrointestinal system, to name a few. Long term risks of the procedure include bowel obstruction, vitamin deficiencies and malnutrition, and stomach perforation.
We appreciated the detailed breakdown of the methodology behind the study, often skipped in these types of releases. The release says:
The study looked at 71 women with a mean age of 44.2 years and a mean body mass index (BMI) of 50.9. Women are considered obese at a BMI of 30 and morbidly obese at 40 (which is typically about 100 pounds over a woman’s ideal body weight), yet almost a third of women presenting for bariatric surgery did not identify themselves as obese.
The study looked at the effects of bariatric surgery in a relatively short timeframe, one to three years after surgery. A total of 68 participants underwent the procedure; two opted out of the surgery, and another died of a heart condition prior to surgery.
Note that the release explains that the study “looked at the effects of bariatric surgery in a relatively short timeframe”. The release signals one of the caveats of the study, that it does not capture the long-term health effects of the surgery.
Later in the release, in referring to a result related to a possible effect from surgery on cancer, the release says:
“We’re talking about small numbers, really tiny numbers” of study participants, Modesitt said, noting one limitation of the study. “So I could never say that effect is definitive, but it is suggestive, given that we know already the incredibly strong link between endometrial cancer and obesity.”
Because this finding did make it past peer review and into the published article, we think it’s worth mentioning and that the caveats provided are sufficient.
The release does not engage in disease mongering and, in fact, provides a nice explanation of what it means to be obese and how some women did not perceive themselves that way.
The authors declared no conflicts of interest in the paper. But one of the study authors was an employee from the company that provided the technology for some of the analyses in the study. This probably was worth a mention.
There is a nice admonition at the end of the release encouraging people to keep their eye on the main way to avoid complications from being overweight or obese: avoid eating too much and exercise more. The release says:
While the study speaks to the transformative effect bariatric surgery can have, Modesitt urged people to avoid gaining weight in the first place and for those seeking to lose weight to exercise and eat more healthily before turning to surgery. “We really should be working on diet and exercise from the get-go in our entire society, starting with our children. And exercise does seem to be protective — even if you don’t lose all the weight, it absolutely has beneficial effects,” she said. “There are lots of studies showing if you exercise, it improves your insulin, your glucose, all of those sorts of things that go along with the cancer-causing effect. Almost everybody agrees adding exercise would be wonderful and improve health on many levels. But losing excess weight would also be good.”
It is clear from the release that the participants underwent a standard bariatric surgery and that these procedures are available. The release could have specified the criteria used to determine who is eligible for such procedures and whether insurance will cover it.
The findings are not presented as novel, and, in fact, are in some cases placed in the context of the larger body of research. For example, the release says:
“The study results demonstrate that there is a huge alteration, but I don’t even know what to say about that, except it is really new and intriguing area to look at in the link between obesity and cancer. For example, before groundbreaking work by Dr. John Marshall at UVA in the past, no one knew that ulcers were from bacteria. Who knows what role the gut bacteria play in promoting obesity, but metabolic parameter/markers of the bacteria definitely changed after [study participants] lost weight.”
This news release gets ahead of itself with the headline as noted above. The claim of a “dramatic” cancer-prevention benefit is just not tenable. The researchers found that precancerous changes resolved in a small number of women, and that there was a “huge alteration” in these women’s gut bacteria. But as the study author readily admits, it’s not clear whether such changes in gut bacteria have any relationship at all to cancer risk. Similarly, all the other outcomes (weight loss, glucose/insulin levels) may have a relationship with cancer, but whether the impact of surgery is enough to affect actual cancer rates is unknown. With so much uncertainty, why frame these results as a “dramatic” benefit in the headline?