By Andrea McBeth, ND
When Cancer Becomes Personal, Everything Changes
For years, I worked in cancer research, studying the science of tumors, immune responses, and the ever-evolving world of oncology. I saw firsthand how research pushes the boundaries of medicine—how breakthroughs in immunotherapy were shifting cancer from a death sentence to a chronic, even curable, condition. But I also saw something troubling: a disconnect between cutting-edge science and real-world patient care.
Then, that divide became personal when my sister was diagnosed with cancer. Suddenly, I wasn’t just a doctor or researcher—I was a sister, an advocate, and a human grasping for answers. The complexities of oncology, once fascinating in a lab setting, now felt overwhelming, frustrating, and painfully slow. The question wasn’t about mechanisms or clinical trials anymore; it was simply:
How do I help the person I love survive and reduce her suffering?
One thing became clear to me: Patients aren’t getting the whole picture when it comes to preparing their bodies for treatment, particularly with immunotherapy. The system moves slowly, and much of the basic science has yet to translate into standard protocols. The microbiome—our gut ecosystem—plays a profound role in immunotherapy response, but it remains an afterthought in most oncology settings, just like nutrition and other supportive care strategies that lack funding and institutional momentum.
Meanwhile, patients undergo surgery, chemotherapy, and antibiotics before ever reaching immunotherapy—all of which can disrupt the gut microbiome and diminish the very immune response immunotherapy relies on. These treatments are often necessary, but they also strip away key microbial allies that could have improved their chances of response to immune checkpoint inhibitors (ICIs).
The research is there. The data is clear. But most patients don’t know this—including many oncologists.
That’s why this conversation matters. Advocacy is essential, and knowledge is power—especially when the system hasn’t yet caught up to the science.
The Science: Why the Microbiome Matters in Cancer Therapy
We now understand that gut microbes regulate the immune system, influencing everything from inflammation to T-cell activation. That means they also impact how well a patient responds to cancer treatment—especially immunotherapy.
Immunotherapy, specifically ICIs like nivolumab (anti-PD-1), work by removing the brakes on the immune system, allowing T-cells to attack tumors. But here’s the catch: Some patients respond incredibly well, and others don’t.The difference? In many cases, it’s their gut microbiome.
Patients with healthier microbiomes respond better to immunotherapy. A growing body of research, including work by Dr. Jennifer Wargo at MD Anderson, has confirmed that gut microbiota composition predicts ICI response. Her team found that:
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Higher microbiome diversity is linked to better survival and response rates.
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Certain beneficial bacteria—like Faecalibacterium prausnitzii, Akkermansia muciniphila, and Ruminococcus spp.—are more abundant in responders.
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Patients who had taken broad-spectrum antibiotics before immunotherapy had markedly worse outcomes.
This aligns with findings from Dr. Harry Sokol, whose research on Faecalibacterium prausnitzii has revealed its immunomodulatory potential. His work shows that:
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F. prausnitzii enhances IFN-γ production and T-cell activation, boosting the immune system’s ability to fight tumors.
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PD-L1 expression is modulated by gut bacteria, potentially affecting how well checkpoint inhibitors work.
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Even bacterial cell wall components, rather than live bacteria alone, can stimulate antigen-presenting cells and influence immune response.
The Problem: Most Patients Start Immunotherapy with a Damaged Microbiome
Despite this compelling data, oncology protocols do not yet integrate microbiome support in any standardized way. Patients typically start immunotherapy after months of microbiome-depleting treatments, such as:
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Surgery & Hospital Stays: Exposure to antibiotics, stress, and diet changes disrupt gut flora.
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Chemotherapy: While it targets cancer cells, it also damages gut epithelial integrity and alters microbial composition.
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Broad-Spectrum Antibiotics: These are often necessary but wipe out beneficial bacteria, including those that could help a patient respond better to ICIs.
By the time a patient starts immunotherapy, their microbiome—the very system that could be an ally in their response—is often severely compromised. This is a missed opportunity.
The Solution: Supporting the Microbiome Before & During Immunotherapy
Here’s the good news: we can take action. Patients and clinicians alike can integrate microbiome support strategies to improve treatment response and overall well-being.
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Nutrition: High-Fiber, Whole-Food Diets Improve Immunotherapy Response
Dr. Wargo’s research, along with data from Jiang et al. (2025) and Radoš et al. (2025), confirms that:
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Patients consuming ≥ 20 grams of fiber per day have a 5x greater likelihood of responding to immunotherapy.
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Prebiotic-rich foods (legumes, oats, leafy greens) selectively feed beneficial microbes, promoting a pro-immunotherapy gut profile.
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Fermented foods (kimchi, sauerkraut, kefir) introduce microbial diversity and support gut-immune crosstalk.
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Avoiding low-fiber, processed diets is beneficial as they are correlated with poorer ICI responses and increased inflammation.
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Avoid Unnecessary Antibiotics Before Immunotherapy
If antibiotics must be used, consider:
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Targeted antibiotic selection over broad-spectrum whenever possible.
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Probiotics or postbiotics afterward to help restore microbial balance.
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Spacing antibiotics away from ICI initiation if clinically feasible.
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Postbiotic & Probiotic Support
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Fecal Microbiota Transplant (FMT) has been shown in clinical trials to restore ICI response in patients who had previously failed.
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Postbiotic formulations (microbial metabolites or inactivated bacterial products) may help mimic the benefits of a healthy microbiome.
Conclusion: Knowledge is Power, Advocacy is Key
I learned early in my work—and even more profoundly through my personal experience advocating for my sister—that the best outcomes happen when medicine is complementary, not contradictory. The most effective care isn’t about choosing between conventional and integrative approaches—it’s about understanding where the system is incomplete and ensuring that patients and the people you care about get the most comprehensive support possible.
This is especially true when it comes to the microbiome’s role in immunotherapy. The science is there: gut health directly impacts how well patients respond to treatment. Yet, oncology has been slow to integrate this knowledge into standard protocols. That means that patients are often left to navigate these gaps on their own—without guidance on how to restore their microbiome after chemotherapy, surgery, or antibiotics before starting immunotherapy.
But this isn’t about rejecting conventional medicine—it’s about advocating for yourself within an imperfect system. It’s about knowing where implementation gaps exist—like microbiome health—and working with your care team to make sure every possible tool is used to improve your chances of success. Research has shown time and time again that high-fiber diets, prebiotics, and microbiome restoration strategies can make a real difference in immunotherapy outcomes. The challenge is that this information isn’t always made accessible.
And that’s the hard part—both emotionally and intellectually. Cancer treatment is already overwhelming. Navigating different sources of information, deciding what matters, and advocating for additional support can feel like a burden when all you want to do is focus on healing. But this is where knowledge becomes power. It allows you to fill in the gaps, ask the right questions, and take meaningful steps to support your body through treatment.
This isn’t just about the microbiome—it’s one of many examples where having multiple perspectives, integrating co-care, and looking beyond the standard protocol can improve long-term outcomes. Whether it’s nutrition, supplements, or other supportive strategies, there is room for both traditional and integrative approaches to work together.
Cancer care isn’t just about survival—it’s about giving every patient the best possible chance to thrive. That means using every tool at our disposal, including the knowledge that the microbiome is not just an afterthought—it’s an ally. So if you or a loved one is preparing for treatment, ask questions, seek information, and advocate for microbiome support. Because in this fight, science and patient advocacy must go hand in hand.
References:
📖 Review Articles: Jiang et al. (2025) & Radoš et al. (2025)
📖 Harry Sokol’s YouTube Lecture on Faecalibacterium prausnitzii
📖 Jennifer Wargo’s YouTube Lecture on microbiome & cancer immunotherapy