For years, clues pointed to the gut microbiome as a key factor in cancer treatment outcomes. Recent advances in gene sequencing are now clarifying its influence on how patients respond to therapy.
At City of Hope, this clarity has catalyzed a more comprehensive model for microbiome science in cancer care. We define the microbiome as the last discovered organ—one that can be characterized and monitored clinically and integrated into a framework that spans measurement, intervention, and clinical decisionmaking.
Just as we routinely assess kidney, liver, or cardiac function, we are embedding microbiome sampling, biobanking, and analysis across our national clinical trials network. This approach allows us to better understand patient-to-patient variability in treatment outcomes and to identify microbial and metabolic signatures that predict patient response, infection risk, and immune toxicity.
City of Hope is uniquely positioned to accelerate the translation of these solutions from the laboratory to the bedside, supported by onsite manufacturing capabilities and an integrated commercialization infrastructure that enables rapid development, testing, and clinical deployment of novel microbiome-based therapies.
Our path forward is shaped by key findings our scientists have generated over the past decade, informed by extensive study of immune reconstitution in patients undergoing allogeneic hematopoietic transplantation.
Although even modest dietary changes can reshape the microbiome within 48 hours, diet remains poorly measured and undervalued in oncology.
As one of the world’s leading centers for this highly specialized procedure, City of Hope cares for a large, deeply characterized transplant population, enabling our researchers to observe how disruption of the gut microbiome, often driven by broad-spectrum antibiotic use, alters immune recovery, therapeutic response, and clinical outcomes, including potentially deadly risks such as graft-versus-host disease and serious infections.
Research led by City of Hope and others has demonstrated that antibiotics and diet are among the most powerful determinants of microbiome health. This recognition has driven the development of strategies to select antibiotics that remain effective against life-threatening infections while minimizing collateral injury to the microbiome.
These insights prompt us to apply microbiome science to understand why treatments succeed or fail and to actively improve them, enhancing treatment response, reducing toxicity, and extending survival and quality of life for patients with cancer.
Bugs as drugs
City of Hope is advancing research on diet as a modulator of treatment outcomes. Recent City of Hope studies suggest that high-fiber diets can support beneficial bacteria that influence immune tone through microbial metabolism, including the production of anti inflammatory short-chain fatty acids that preserve gut integrity.
Although even modest dietary changes can reshape the microbiome within 48 hours, diet remains poorly measured and undervalued in oncology. City of Hope is investing in tools and partnerships to better capture dietary data and evaluate how targeted nutritional strategies tailored to each patient’s microbiome can improve immune recovery, treatment tolerance, and survival. In this context, nutrition represents one of the most accessible and scalable opportunities to influence cancer care.
Together, these efforts reflect our deliberate strategy to integrate microbiome science into routine cancer care, including:
- Investigating the feasibility of high-fiber diets for patients undergoing transplantation
- Evaluating fecal microbiota transplantation for patients receiving immunotherapy
- Developing defined, reproducible microbial therapies compared with minimally manipulated donor products
- Using microbiome data to guide antibiotic stewardship and supportive care
- Integrating microbiome science across departments to advance personalized cancer care
- Implementing AI-enabled tools to track dietary intake in real time
Further studies to understand how the gut shapes baseline immune function and inflammation may also improve prevention, risk stratification, and early detection—areas where cancer care still falls short. Looking ahead, this comprehensive approach to microbiome science is setting the stage for personalized interventions tailored to each patient’s diet, microbiome, and immune features. That future is already being built at City of Hope, where we are creating a multidisciplinary, scalable blueprint for the next era of cancer care.
City of Hope® is one of the largest and most advanced cancer research and treatment organizations in the U.S. To learn more about City of Hope, visit: www.cityofhope.org.
Discover the latest innovations in cancer research on City of Hope’s new podcast, “On the Edge of Breakthrough: Voices of Cancer Research.” Available on Spotify, Apple Podcasts and at cityofhope.org/edge-of-breakthrough.
