Interview by Lauren LeBano
The results of a pilot study suggest that percutaneous CT-guided cryovagotomy is a safe and feasible procedure that may help patients with mild-to-moderate obesity lose weight. The procedure uses CT guidance and argon gas to freeze the posterior vagal trunk, a nerve that contributes to communication between the brain and stomach regarding hunger. After being followed for 90 days, the 10 participants in the study had decreased appetite and overall weight loss of 3.6% of initial body weight. J David Prologo, MD, the study’s lead author, joined us to discuss the results and what they may mean for patients and the interventional radiologists treating them. Dr Prologo is an interventional radiologist at Emory University School of Medicine in Atlanta, Georgia, and he presented the results of the pilot study at the 2018 Society for Interventional Radiology meeting in Los Angeles, California.
VDM: Why did you decide to undertake this study?
Dr Prologo: I’m personally fascinated with the phenomenon of attrition, which is how people often start diets and then quit shortly thereafter. Strong people will start a diet with great intentions on Monday and by Thursday they are unable to continue. We often hear that a lack of willpower is the reason, but I don’t buy that explanation. That’s why we did this study. It’s not willpower that causes people to stop their diet; rather, it’s overwhelming survival and food-seeking signals that cause people to give up. If we can interrupt those bodily signals, then we can do two things. We can help people stay on track with their diets and accomplish their weight-loss goals, and we can also show that willpower is not a factor and that there is no basis for fat shaming.
VDM: Tell us about setting up the study and what were you hoping to find.
Dr Prologo: As interventional radiologists, we use image guidance to guide needles and probes to certain places in the body. We set up the study with the intention of applying our existing interventional radiology skillset to the problem of obesity. We use cryoablation and cryoneurolysis to treat pain, and we freeze nerves to stop pain signals, so we wanted to use CT guidance in interventional radiology to guide a probe to the vagus nerve, which carries hunger. This is a new approach, so it’s first necessary to prove that the procedure is safe, which was the primary aim of the study.
VDM: How does this procedure compare to gastric embolizaton?
Dr Prologo: Gastric embolization is similar. There is a hunger hormone in the stomach called ghrelin, and it is released when people restrict calories. Bariatric artery embolization is one way to decrease that response. Cryoablation of the vagus nerve is similar in that we are trying to reach the same goal. We want to decrease the body’s backlash to calorie restriction but by blocking a different path, a neural path. For me personally, this was a natural segue, as I frequently perform cryoneurolysis to treat pain.
VDM: Are there any other groups conducting similar research?
Dr Prologo: Right now, I think we’re the only ones doing this procedure. The most similar procedure is the vagotomy, which is a historical surgical procedure. It was part of antiquated ulcer operations, and people did lose weight. There is also a surgical implantation device in which people are trying to modulate the signals in this nerve, but that option has all the morbidities that go along with surgeries and implanted devices.
VDM: Any cautions/encouragements for others interested in this procedure?
Dr Prologo: Although we did not need an IDE because these probes are approved for cryoneurolysis, it’s important to perform this procedure in the structure of a study with proper IRB and FDA oversight. This enables us to keep everyone safe and to prove that these findings are durable in the long run.
We have been encouraged that we accomplished our goal of proving the procedure is feasible and safe. We’ve also had encouraging ancillary findings that show that every patient is reporting decreased appetite. Additionally, the cohort average weight loss was on a promising trajectory, and patients are reporting feeling fuller faster. It’s exciting to have patients who have struggled with weight loss their entire lives come back, hug you, say thank you, and say the procedure has changed for the better how they feel when dieting.
VDM: How do you determine which patients are good candidates for the procedure?
Dr Prologo: The criteria are strictly defined. We wanted patients who had BMIs between 30 and 37 and who had failed previous attempts to lose weight. After doing the pilot study, I want to add that we should select for patients who have difficulty losing weight because they feel hungry. That type of selection might feel intuitive, but in fact there is a small subpopulation of folks who continue to eat even after they no longer feel hungry. In that population, taking away their hunger won’t help, so it’s better to select for patients who struggle with the feeling of hunger.
VDM: Could patients still have gastric bypass after undergoing this procedure?
Dr Prologo: Technically speaking, folks with a BMI 30 and 35 don’t qualify for gastric bypass, but the cryovagotomy procedure itself would not preclude them from that.
VDM: Was there anything surprising about your findings?
Dr Prologo: I think the most surprising aspect of our results was finding that some patients felt fuller faster. We anticipated that people would feel less hungry and they would lose weight, but we were surprised that many of them reported eating less at each sitting—not necessarily because they were less hungry—but because they were feeling fuller faster.
VDM: What are the main takeaways for your colleagues and others?
Dr Prologo: It’s important for interventional radiologists to know that the skillset we have is great by itself but is also applicable to new problems. We need to keep our eyes on the horizon and see where we can apply our skillset to other types of clinical problems.
Another personal take-home point is that our study shows that fat shaming is unfounded based on science. Obesity is a disease like all the other diseases. We don’t shame anyone for having heart disease or cancer, so we need to stop shaming people for obesity, too.
J Prologo, S Cole, S Horesh Bergquist, et al. Percutaneous CT guided cryovagotomy for the management of mild - moderate obesity: a pilot trial. Abstract #2186. Presented on March 18, 2018. Society of Interventional Radiology Meeting. Los Angeles, California.