Dip in gut microbiota diversity linked to chemo-related weight gain in breast cancer patients

Researchers from the University of Alberta found patients with breast cancer had significantly more weight gain and greater disruptions in their gut microbiome when treated with chemotherapy than those treated with hormone therapy. These patients also had changes in where fat was located on their bodies. The finding suggests that future interventions to address weight gain following chemotherapy could target the gut microbiome. “Changes in the bacterial populations within the gut directly correlate with unhealthy weight gain and increased body fat composition in breast cancer patients who were treated with chemotherapy,” said lead author Dr. John Walker, associate professor in the University of Alberta faculty of medicine and dentistry and head of medical oncology for northern Alberta at the Cross Cancer Institute in Edmonton. A 2020 survey from Australia suggests 50% of people with breast cancer are overweight or obese before diagnosis, but that percentage creeps up to 67% after treatment. This increase is not fully explained by changes in diet or exercise during treatment. The survey results were published in BMC Medicine. “People tend to be a little less active during and after chemotherapy but they also tend to significantly reduce their caloric intake,” Dr. Walker said in a University of Alberta press release. “Our study shows there is a more nuanced explanation. There’s something unique about this modulation of the gut microbiome for breast cancer patients who receive chemotherapy.” Read: Soda sweetener aspartame now listed as possible cancer cause. But it’s still considered safe Dr. Walker and colleagues followed 40 patients with early-stage breast cancer who were prescribed chemotherapy, hormone therapy, or both, after genetic analysis of their tumours. The patients provided stool and blood samples before surgical removal of their tumours, before and after chemotherapy or hormone treatment and one year after diagnosis. Patients also had dual-energy X-ray absorptiometry (DEXA or DXA scans) to monitor body composition. Patients who had chemotherapy had changes in the populations of 47 different microbes in the gut following chemotherapy, but these changes were not detected in the patients who received hormone therapy. They also had significantly higher markers of inflammation and evidence of inflammation in the colon. Patterns of weight after treatment were significantly different between the two treatment groups. Patients receiving chemotherapy gained an average of 0.15% of body mass per month, where patients on hormone therapy lost an average of 0.19% of body mass per month. Weight gain was highest for patients who were premenopausal and less than 60 years old. The DXA scan results revealed that patients treated with chemotherapy lost more muscle mass and gained more abdominal fat than those treated with hormone therapy alone. This type of fat deposition (android fat deposition) is a risk factor for metabolic disease. Other studies have shown that people with more android fat deposition have less diversity in their gut microbiome, the researchers noted in their paper. Read: It’s time to leave the Paleo Diet in the past: Recent studies have failed to support its claims These changes in body composition after chemotherapy treatment suggest that even if the weight is lost, the changes in body-fat composition may remain. Weight-loss alone may not be sufficient treatment to reduce any risk of future metabolic disease. Follow-up treatment might be needed to address weight gain after chemotherapy, the researchers suggest. For example, fecal transplants or GLP-1 agonists may help treat obesity in this patient population. “Breast cancer is an unparalleled success story in medicine. We see cure rates over 90% today, so survivorship is now equally important,” Dr. Walker said. “We want to ensure that in survival, our patients aren’t then dealing with the metabolic consequences of weight gain during treatment.” The paper was published in BMC Medicine. Read: First pill for fecal transplants wins U.S. FDA approval

Dip in gut microbiota diversity linked to chemo-related weight gain in breast cancer patients

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