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Weight loss surgery tied to a lower risk of blood cancer in a new study. Image credit: Guillermo Arias/AFP via Getty Images.
  • Obesity is a risk factor for many cancers, and the number of cancers that were previously only typically seen in people over 50 have an increasing prevalence in younger people with obesity.
  • Diet and lifestyle interventions are not always successful in treating obesity and reducing cancer risk in the long term, and bariatric surgery has been shown to reduce cancer rates in people with obesity.
  • Now, a team of researchers from the University of Gothenburg in Sweden has shown that bariatric surgery could reduce the risk of blood cancer in women, in a cohort of Swedish people.

According to the Centers for Disease Control and Prevention (CDC), 13 cancers are linked to obesity, and now, research suggests that blood cancers could be added to that list.

Cancers linked to obesity make up 40% of cancers diagnosed in the United States, and women are disproportionately affected.

Of the 13 cancers linked to obesity, the most common is breast cancer in women at the postmenopausal stage. Others include uterine and ovarian cancer, and some evidence suggests that women with obesity are at higher risk of cervical cancer, too.

The reasons underpinning the difference between men and women are not entirely understood, though some researchers think that the relationship between insulin, sex hormones, and molecules that play a role in inflammation called cytokines could play a role.

Excess adiposity increases the risk of insulin insensitivity, where the cells are less receptive to the hormone’s presence.

This makes the body produce more insulin, and eventually the insulin producing cells in the pancreas become unable to keep up with the amount of insulin needed by the body, causing blood sugars to rise.

This leads to type 2 diabetes, which is associated with an increased risk of cancer, and while both share many underlying risk factors, the mechanisms underpinning the link are still the focus of research.

Dr. Magdalena Taube recently led a team of researchers from the University of Gothenburg in Sweden to investigate the rate of blood cancer in people who had undergone bariatric surgery.

Their study results appear in The Lancet.

Dr. Taube told Medical News Today in an interview:

“It’s like the insulin [is] driving the female cancers, and since insulin and estrogens can regulate the expression of each other, […] [they] might be cross-talking, making women more susceptible to obesity, and the effects of obesity, since obese women are at risk of higher insulin levels.”

Because of the increased risk of cancer faced by people with obesity, one long-term health benefit of bariatric surgery could be a lower cancer risk.

In order to quantify this, Dr. Taube and her team followed up a group of 4,047 individuals with obesity in Sweden, half of whom had bariatric surgery and half of whom acted as matched controls and did not.

All participants were enrolled between September 1, 1987 and January 31, 2001 in the Swedish Obese Subjects (SOS) intervention study. This study was originally set up to compare the death rate of people with obesity who had bariatric surgery compared to those who did not.

For this analysis, the team looked at the cancer rates in this group over a 33 year follow-up period, and found that bariatric surgery decreased the incidence of blood cancer risk in women by 56%. The same decrease in risk was not seen in men.

Most of the blood cancers detected during the study were lymphomas, and when just this type of blood cancer was looked at, a decrease in risk of 55% was found in patients who had bariatric surgery.

Dr. Taube said that while a decision was made in 1991 to place a threshold for bariatric surgery at a body mass index (BMI) of 34 for men, and 38 for women, the cohort they looked at had similar BMI across the sexes. BMI is a calculation made using weight and height to infer adiposity, or the amount of fat a person has.

The results added to existing research that suggest blood cancer could be considered a form of obesity-linked cancer, and could promote the use of bariatric surgery as a way to decrease cancer rates in people with obesity, the study authors said.

“It’s not only us, many retrospective studies have shown that bariatric surgery reduces cancer risk. And if we consider that basically the obesity pandemic is still ongoing, and we have more and more early onset cancers,“ said Dr. Taube.

“So people below 50 years of age develop the kinds of cancers that normally older people get,“ she further explained. “[T]herefore, it’s so important to try and reduce the cancer risk because these young people with obesity will probably develop cancer, therefore, bariatric surgery should be more considered in the prevention of cancer, actually.”

While the current paper did not look at the mechanisms behind the link between obesity and sex to blood cancers, researchers suggested that a mechanism called mutation-driven clonal hematopoiesis could be behind the findings.

Clonal hematopoiesis explains the phenomenon whereby mutations that occur naturally as we age, take place in the stem cells that turn into blood cells. Some of these mutations mean that certain types of stem cell replicate more than others, and the result is that over time the population of blood stem cells a person has becomes less varied. This has been linked to blood cancer and cardiovascular disease.

This process is thought to be accelerated by obesity, and previous research has shown that bariatric surgery can reduce the rate of mutation-driven clonal hematopoiesis.

Dr. Taube said the team had looked at this phenomenon over 20 years in the cohort and found there is an association between clonal hematopoiesis and insulin and high density lipoprotein cholesterol levels.

“We want to look at participants in the SOS study who is carrying a mutation or not, and see if that could be linked to cancer risk. That is so that we can actually pursue that line of inquiry,” she said.

Dr. Mir Ali, a bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA who was not involved in this research, told MNT that “[t]his paper is another reaffirmation that obesity increases the risk for cancer, and bariatric surgery can safely and effectively reduce that risk.”

“I strongly agree with the authors that there may be several mechanisms that increase cancer risk, including chronic inflammation, but more research is needed to delineate these mechanisms further,” he added.