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Dr. Brendan Guercio received a 2023 Interdisciplinary RCC Focus Award for research on “Associations of diet with the gut microbiome among patients with advanced/metastatic RCC receiving immune checkpoint inhibition.” This award was supported by a gift from the Michael and Ina Korek Foundation. Dr. Guercio is an Assistant Professor in the Department of Medicine at the University of Rochester Medical Center’s Wilmot Cancer Institute. We spoke with Dr. Guercio about his research and it’s impact on people with kidney cancer.

Can you briefly summarize your project?

Immunotherapy, which teaches the immune system to fight cancer, has revolutionized the care of patients affected by kidney cancer.  Yet while many patients with kidney cancer respond to immunotherapy very well, some patients unfortunately do not. And even patients who respond well to immunotherapy at first may eventually stop responding and experience cancer progression. So it is incredibly important for cancer doctors and researchers to find ways to make immunotherapy work even better for our patients.

The gut microbiome (i.e., the bacteria and other microbes that live in our gut) has emerged as an important factor that may influence how well patients respond to immunotherapy.  In a pilot study that I conducted with my collaborators at Memorial Sloan Kettering Cancer Center, we found a strong signal suggesting that more dietary fiber is associated with better immunotherapy efficacy among patients with kidney cancer.  The goal of the current project, which the Kidney Cancer Association has generously supported, is to confirm whether or not our preliminary finding is true and also determine how exactly dietary fiber is interacting with the gut microbiome to influence the immune system and the effects of immunotherapy.

What do gut bacteria have to do with cancer?

Multiple studies have now shown that specific types of gut bacteria are associated with benefit from immunotherapy.  In fact, two small trials for patients with advanced kidney cancer treated with immunotherapy have now shown that addition of a probiotic (a specific type of bacteria that patients took orally) may improve control of kidney cancer by immunotherapy.  But how exactly the gut bacteria are influencing the immune system and immunotherapy is not entirely understood.  Some experts believe that gut bacteria are producing specific molecules that help the immune system work better.  For example, when good gut bacteria digest the fiber that we eat, they generate molecules called short-chain fatty acids.  These short-chain fatty acids are known to have beneficial effects on the immune system.  So our research group thinks that eating more dietary fiber may feed the good gut bacteria and help them produce more short-chain fatty acids to help the immune system better fight kidney cancer.  And that is what we are trying to test with our current project.

Managing cancer through diet and nutrition is very exciting to many people. However, there is also a lot of bad science and misinformation on this subject. Do you notice this among patients and families?

Absolutely. While we know from many good scientific studies that diet and nutrition are important to health in general, it is also important to note that nutritional supplements and other dietary strategies that are marketed to patients and their families are not usually regulated by government agencies or other expert organizations. As a result, there is little that can be done to protect the public from misinformation about supplements and nutrition. So it is essential for healthcare providers and scientists to help patients find accurate information about diet and nutrition. Before following advice seen on places like social media or commercials, I always recommend that patients have a discussion with their physicians. The proliferation of bad science and misinformation about diet and nutrition is also an important reason for researchers to do good science investigating diet and nutrition, so that we can use good information to protect patients and their families from misinformation.

How would you explain what is exciting about manipulating gut bacteria to enhance treatment efficacy while managing patient expectations about the potential for diet to impact their cancer outcomes?

I would first emphasize, that based on everything we have learned so far, diet and nutrition may be important, but they are not a substitute for standard treatments like immunotherapy, which are essential for many of our patients with advanced kidney cancer. But if we can help standard treatments like immunotherapy work better just by helping patients to eat the right foods, then that would be an enormously exciting way to improve outcomes for our patients without necessarily adding significant side effects the way new medications sometimes do. I would also emphasize that while early studies like our pilot study have shown promising signals for how diet might help immunotherapy work better, it is also important for us to confirm these preliminary findings with larger studies and ultimately with randomized clinical trials.

What motivates you?

Just like many of my other colleagues in oncology and cancer research, my primary motivation is a desire to better help the patients we take care of every day. In recent decades, the field of oncology has made amazing strides in finding new ways to help patients with kidney cancer live better and longer than ever before. But there is still a lot of work left to be done and I am honored to be a small part of the enormous effort underway to make treatments even better for patients affected by kidney cancer.

What else do you want others to know about your work?

I would encourage patients to become a part of the movement to improve cancer care by participating in clinical research, because research is the only way that we can move the ball forward in the fight against kidney cancer. Healthcare providers understand that receiving a new cancer diagnosis or starting a new cancer treatment can be overwhelming for patients, and so enrolling in clinical research studies simultaneously can feel very daunting to patients and their families. And yet it is amazing to see that so many patients choose to participate in research anyway. The courage that our patients show every day in their fight against cancer and their willingness to participate in studies to help future generations of patients inspires my colleagues and I to work even harder every day. We are eternally indebted to our patients for going the extra mile to participate in research so that we can all advance the field of cancer care together.

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