What Determines Whether Your Immunotherapy Actually Works? A Precision Guide to Optimizing Your Response

By Dr. Lena Suhaila, ND, FABNO

Your oncologist chose the drug. They chose the protocol, the dosing schedule, and the monitoring plan. What almost nobody has looked at is whether your biology is actually positioned to respond to it. That is not a criticism of your oncology team. They are working within a model that was not designed to ask that question. But the question is real, it is measurable, and in many cases, the answers are profoundly actionable.

If you are on immunotherapy right now, or preparing to start, what follows is the conversation I wish every patient had access to before their first infusion.

The Immune Cells Your Treatment Depends On

Checkpoint inhibitors work by releasing the brake on your immune system, specifically on the T cells that are capable of recognizing and destroying cancer cells. The drug does its part. But whether there is a robust, functional immune population for it to work with is a completely separate question, and it is one that rarely gets asked with any precision in a standard oncology appointment.

The neutrophil to lymphocyte ratio, which your doctor can calculate from a standard CBC with differential, is one of the most underutilized prognostic markers in immunotherapy. A high ratio, meaning a relatively elevated neutrophil count compared to lymphocytes, is consistently associated with worse outcomes in patients receiving checkpoint inhibitors across multiple cancer types. It reflects a systemic inflammatory state that works against the kind of targeted immune activation immunotherapy depends on.

Your absolute lymphocyte count matters enormously, and it needs to be tracked longitudinally across your treatment cycles, not just measured once at baseline. If your lymphocyte pool is being depleted over time, the specific CD8 cytotoxic T cells that your checkpoint inhibitor is designed to activate are being depleted along with it. The drug is working in an increasingly compromised environment, and nobody may be connecting those dots unless someone is specifically looking for them.

The CD8 T cell count itself, where testing is available, gives you an even more direct picture of the cytotoxic immune capacity your treatment is relying on. These are the soldiers. It is worth knowing how many you have and whether that number is holding steady, declining, or recovering between cycles.

None of these are exotic tests. The question is whether anyone is reading them with this clinical lens.

The Nutrient Foundation, and Why Assuming Is Not Good Enough

There is a meaningful body of research showing that vitamins A, C, D, E, B12, riboflavin, folic acid, iron, zinc, and selenium all have direct immunomodulatory functions that are relevant to how well your immune system responds to checkpoint inhibitor therapy. Several of them also appear to play a role in reducing the severity of the inflammatory side effects that immunotherapy can trigger in healthy tissue. In a patient who is depleted in multiple micronutrients, which is not uncommon at the time of a cancer diagnosis, the immune system is already working at a disadvantage before the drug is even administered.

But here is what I want you to understand about supplementation in this context. Taking a supplement and getting what you think you are getting from it are two completely different things, and your genetics determine a great deal of that gap.

Take vitamin A as an example. Most supplements and many foods contain beta carotene, which is a precursor that your body is supposed to convert into the active form of vitamin A, retinol palmitate, that your immune cells actually use. The enzyme responsible for that conversion is encoded by the BCMO1 gene. A significant percentage of the population carries a variant of this gene that substantially impairs that conversion, meaning that if you are taking beta carotene and assuming you are getting vitamin A, you may be getting very little of the active form your body needs. You need retinol palmitate directly, not a precursor that your genetics prevent you from efficiently processing. Without testing, you would never know.

The same principle applies to omega-3 fatty acids. If you are relying on plant-based sources of omega-3, flaxseed, walnuts, chia seeds, hemp seeds, you are consuming ALA, a short-chain fatty acid that needs to be converted into EPA and DHA, the long-chain forms that your cell membranes, your inflammatory signaling pathways, and your mitochondria actually depend on. The FADS1 gene encodes the enzyme responsible for that conversion. Variants in this gene are common, and they significantly reduce conversion efficiency, which means a patient eating what looks like a perfectly omega-3 rich diet may still be profoundly deficient in EPA and DHA at the cellular level. This matters for immune function, it matters for cell membrane integrity, and as we will come to in a moment, it matters deeply for mitochondrial health.

Vitamin D deserves particular attention because the gap between what conventional medicine considers sufficient and what actually supports optimal immune function in the context of cancer is significant. Testing your 25-hydroxyvitamin D level and maintaining it in a genuinely therapeutic range, not just out of deficiency, is a concrete and measurable way to support the immune competence your treatment depends on.

Zinc and selenium are both essential to immune cell function, and both have a narrow therapeutic window. Too little impairs the immune response. Too much, particularly with selenium, creates its own toxicity. The ratio between them and their interaction with other minerals matters. This is precisely why testing before supplementing is not optional; it is the only rational approach.

What Your Genes Are Telling You About Your Nutritional Needs

Nutrigenomic testing looks at the genetic variants that determine how your individual body absorbs, processes, activates, and utilizes the nutrients that support immune function. The BCMO1 and FADS1 examples above are two of the most clinically relevant in this context, but they are far from the only ones.

MTHFR variants, which are extremely common, impair the methylation pathway that is essential for immune cell proliferation, DNA repair, and the production of glutathione, your body’s primary endogenous antioxidant. A patient with a significant MTHFR variant who is taking standard folic acid rather than the active methylfolate form is not getting what their immune system needs, and standard blood work will not reveal that distinction without someone specifically looking for it.

The broader principle is this: two patients can follow identical dietary and supplement protocols and have completely different biological outcomes based on their genetic individuality. Personalization in this context is not a wellness trend. It is a clinical necessity, and it is now testable with tools like nutrigenomic panels that give a clear picture of where your individual biochemistry needs specific support.

Your Gut Is an Immune Organ

Approximately 70 percent of your immune system lives in and around your gut. The composition of your gut microbiome directly influences how your immune system responds to checkpoint inhibitor therapy, and the data on this has become increasingly compelling. Specific bacterial species, particularly Bifidobacterium longum and Akkermansia muciniphila, have been associated with significantly improved immunotherapy response rates, particularly in melanoma and non-small cell lung cancer. Patients with greater microbiome diversity consistently show better outcomes. Patients with dysbiosis, particularly following antibiotic use, show worse outcomes meaningfully.

If you have had antibiotics recently, if your digestion is compromised, if you have been through chemotherapy that disrupted your gut ecology, your microbiome may need active restoration before or during immunotherapy. Microbiome testing gives you a map of where you actually are rather than where you assume you are. For a deeper look at what the research says about the gut and cancer treatment outcomes, I have written about this specifically, and it is worth reading alongside this article. [INTERNAL LINK: The Gut Microbiome and Chemotherapy: What the Research Says About Your Outcome]

The Mitochondria: The Engine Behind Everything

If there is one biological system that connects almost every thread in this article, it is the mitochondria. These are not simply the energy generators of the cell, though that function alone is critical. They are central to immune cell activation, to the differentiation of T cells into the cytotoxic subtypes that immunotherapy depends on, to the regulation of inflammatory signaling, and to the metabolic flexibility that determines whether your immune cells can sustain the prolonged activity a checkpoint inhibitor is trying to generate.

Mitochondrial function is directly influenced by the nutrients we have already discussed. CoQ10, magnesium, B vitamins, alpha lipoic acid, and the long-chain omega-3 fatty acids EPA and DHA all play specific roles in mitochondrial membrane integrity and electron transport chain function. If your FADS1 variants are limiting your EPA and DHA status, your mitochondrial membranes are working with suboptimal building materials. If your B vitamin status is compromised by MTHFR variants or dietary insufficiency, the energy production your immune cells depend on is impaired at a fundamental level.

This is why the nutrigenomic and micronutrient testing picture matters so much. You are not just optimizing a number on a lab panel. You are supporting the biological machinery that your immune system runs on, and that your treatment depends on to do its job.

What Is Quietly Working Against Your Treatment

There are variables that undermine immunotherapy response that are rarely discussed with patients directly, and I think that needs to change.

Corticosteroids are commonly prescribed alongside immunotherapy, sometimes to manage inflammatory side effects, sometimes as part of an antiemetic protocol, sometimes for other reasons entirely. The problem is that corticosteroids are broadly immunosuppressive. They dampen lymphocyte activity, which is precisely the biological machinery your checkpoint inhibitor is designed to activate. If you are on steroids concurrently with immunotherapy, even short courses, the tradeoff between managing side effects and suppressing the immune response your treatment depends on deserves to be named out loud and discussed explicitly with your team. This does not mean steroids are never appropriate. It means the conversation needs to happen.

Chronic stress and sustained cortisol elevation are directly immunosuppressive through mechanisms that include lymphocyte apoptosis, suppression of natural killer cell activity, and impaired T cell proliferation. This is measurable through salivary cortisol testing and heart rate variability assessment. It is not a soft variable. It has a direct mechanistic connection to how well your immune system can respond to treatment.

Sleep deprivation specifically depletes natural killer cell populations and impairs the lymphocyte function that your checkpoint inhibitor is working to enhance. One night of significant sleep disruption produces measurable changes in immune cell activity. Chronic poor sleep during a treatment course is a sustained biological headwind.

The metabolic environment matters in ways that are often overlooked in oncology. Elevated insulin and chronic glucose dysregulation suppress T cell function through multiple pathways and create a systemic inflammatory environment that works against the targeted immune activation that immunotherapy is designed to produce. Where your metabolic health sits right now is testable and in many cases, significantly improvable, regardless of where you are in your treatment.

Circadian Biology and When You Receive Treatment

Your immune system is not equally active at all hours of the day, and the timing of your immunotherapy infusion appears to matter more than almost anyone in conventional oncology is currently acknowledging. I have written about this in detail, and the evidence, including a phase III randomized trial presented at ASCO 2025, is significant enough that every patient on a checkpoint inhibitor should be aware of it.

Supporting your circadian biology through consistent sleep and wake timing, appropriate light exposure, and meal timing aligned with your biological rhythms reinforces the same immune activity patterns that the infusion timing research is measuring. These are not separate conversations.

Diet as Both Optimization and Protection

A well-formulated ketogenic diet with a high vegetable content does something that is genuinely relevant in the context of immunotherapy and it operates on multiple levels simultaneously.

At the metabolic level it removes the chronic glucose and insulin dysregulation that suppresses T cell function and creates a systemic inflammatory environment. Cancer cells are heavily dependent on glucose through the Warburg effect, and a ketogenic metabolic state selectively disadvantages them while healthy cells, including immune cells, adapt effectively to fat-based fuel. Your healthy cells are considerably more metabolically flexible than cancer cells. A high-fat, very low carbohydrate diet exploits that difference.

At the cellular level, beta hydroxybutyrate, the primary ketone produced during nutritional ketosis, is a direct inhibitor of the NLRP3 inflammasome and suppresses NF-kB signaling, two of the central drivers of the systemic inflammation that can both impair immunotherapy response and amplify the collateral inflammatory damage that immunotherapy can cause in healthy tissue.

And that brings me to something I want to address directly, because it is something every patient on immunotherapy is either experiencing or worrying about. When checkpoint inhibitors release the brake on the immune system, the immune activation is not always perfectly targeted. It can spill into healthy tissue and trigger inflammatory responses in the gut, the lungs, the liver, the thyroid, the skin, the joints, and other organ systems. These are real; they range from manageable to serious, and they are one of the primary reasons patients end up on corticosteroids during treatment.

A dietary pattern that is genuinely anti-inflammatory, rich in vegetables that provide phytonutrients, polyphenols, and fiber alongside the metabolic benefits of carbohydrate restriction, does not eliminate these risks, but it meaningfully reduces the inflammatory substrate that amplifies them. You are essentially lowering the background level of systemic inflammation so that when the immune system activates, it is doing so from a calmer baseline.

This applies before treatment, during treatment, and after treatment. And I want to say something clearly here: it is never too late to move toward this way of eating. If you are already in the middle of a treatment course and your diet has not been what you would want it to be, that is not a reason to wait. The biology responds quickly to dietary change. The best time to start was before diagnosis. The second best time is right now.

Are You Actually Responding? The Case for Molecular Monitoring

Most patients find out whether their immunotherapy is working from a scan. That scan might happen every eight to twelve weeks. In between, you are largely waiting. And if the treatment is not working, you may not know for months.

Circulating tumor DNA testing, through platforms like Natera’s Signatera, offers something qualitatively different. ctDNA testing detects fragments of tumor DNA circulating in the bloodstream and can provide a real-time molecular signal of whether treatment is achieving what it is supposed to achieve. A declining ctDNA level during immunotherapy is a meaningful indicator of response. A rising or persistently elevated signal is a clinically important early warning that the treatment may not be working, weeks or months before that information would appear on a conventional scan.

In the context of immunotherapy, where response can be dramatic in some patients and completely absent in others, having that molecular intelligence between scans is not a luxury. It is a way of ensuring that precious time is not spent on a treatment that is not working when other options might be available.

This is the kind of monitoring that integrative oncology brings to the table alongside conventional care. Not replacing what your oncology team does, but adding a layer of biological intelligence to the decisions being made about your treatment.

The Question Worth Asking

Your immunotherapy is one of the most powerful tools available in modern oncology. Whether your biology is positioned to respond to it, whether your immune cells are robust enough, your nutrients sufficient and correctly matched to your genetics, your mitochondria well-supported, your gut ecology intact, your inflammatory burden low enough, and your metabolic environment favorable, is a separate and equally important question.

These things are testable. They are addressable. And working on them is not something you do instead of your conventional treatment. It is something you do alongside it, so that the treatment you are already receiving has the best possible biological conditions to work in.

It is never too late to move in this direction. Your biology is responsive, sometimes remarkably so, and every positive change you make to the internal environment is a change that works in your favor. Start now.

If you are ready to look at your own biology with this level of precision and build a protocol that is specific to you, I would welcome that conversation.

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References

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