How Cancer Endures Treatment and Rebuilds

Almost every patient I see eventually asks some version of the same question, usually quietly, months into treatment, when a scan comes back worse than the last one. Why does it come back? The medicine was working. Nothing about it changed. What happened?

I want to give you the most honest answer I can, because it is more interesting than the one most people get, and because understanding it changes what questions are worth asking your oncology team.

An uncomfortable finding

Start with something researchers at Bayer published a few years ago while looking for compounds that could target a particular population of tumor cells.

They took breast cancer cells and exposed them to radiation at increasing doses. As you would expect, the total number of living cells dropped, and it dropped further with each higher dose. That is radiation doing its job.

But they were also counting a specific subgroup within those cells, marked by high activity of an enzyme called aldehyde dehydrogenase. That subgroup did not shrink. It grew. At each dose step, the proportion of these cells increased until, at higher doses, they made up roughly five times the share of the surviving population they had before treatment. When the researchers separated the two populations and irradiated each on its own, they confirmed the difference. These cells simply survived radiation better than their neighbors.

Radiation had not only killed cancer cells. It had concentrated the ones best able to endure it.

Why that particular subgroup matters

Researchers call these cancer stem cells, or tumor-initiating cells. The name can mislead, so let me be precise about what it does and does not mean.

Most cells in a tumor, if you isolated a handful and placed them in the right conditions, would not grow into anything. A small subset would. In the same experiments, when researchers placed single cells in each well and watched for a week, the stem-like cells formed new tumor spheres at dramatically higher rates than the others. They can rebuild the whole thing from very few survivors.

So consider the arithmetic. A treatment that kills 99% of a tumor has done something real and worth doing. But if the 1% remaining is disproportionately made up of the cells with the greatest capacity to rebuild and the greatest resistance to the next round, then the tumor that regrows is not the tumor you started with. It is tougher, assembled from the survivors, and it may respond less well to the same treatment a second time.

This is not an argument against conventional treatment. Debulking a tumor matters enormously, and the alternative to killing 99% is not killing any of it. It argues that the job is not finished when the scan improves, and that the remaining fraction deserves as much thought as the fraction we removed.

Four ways cancer survives

The stem-like population is not the only problem. Cancer cells have several well-documented ways of enduring treatment, and four show up consistently across tumor types:

1. Drug efflux pumps: Cells carry transport proteins that push foreign substances back out. This protects you under normal circumstances. Cancer cells overproduce them, so chemotherapy enters and is escorted out before it can work.
2. Efficient DNA repair: Chemotherapy and radiation work largely by breaking DNA. Your healthy cells maintain repair crews for exactly this purpose, since DNA takes damage constantly from ordinary living. Resistant cancer cells amplify those crews until they patch damage faster than treatment creates it.
3. Apoptosis evasion: Healthy cells carry an internal safeguard. Past a damage threshold, the cell shuts itself down in an orderly way rather than dividing with a corrupted blueprint. It is one of the most elegant protections in human biology, and it is why most of us do not develop cancer as often as we do. Cancer cells frequently disable this switch.
4. Microenvironment shielding: A tumor recruits the surrounding tissue, turning the neighborhood acidic, quieting nearby immune cells, and thickening the surrounding matrix. Your immune system may recognize the cancer perfectly well and be unable to reach it, or be chemically persuaded not to act once it arrives.

The part almost nobody mentions

When any cell dies, its nucleus ruptures and spills its contents. What escapes is a mixture of DNA fragments and chromatin, and structurally it resembles foreign genetic material closely enough that neighboring cells cannot reliably tell the difference between debris from a dying neighbor and DNA from an invading organism. They respond as though under attack.

Cells take these particles up. Inside, the particles can reach the nucleus, interfere with repair, and cause the most severe form of DNA damage. They trip inflammation sensors. Research published in 2024 found that particles from dying cancer cells activate immune checkpoints in human lymphocytes, which gives a concrete mechanism for how debris helps a tumor hide.

Now put that beside everything above. Chemotherapy works by killing cancer cells. So does radiation. So does your own immune system. Each of those successes releases a wave of chromatin debris into the neighborhood, and that debris can damage surviving cells, drive inflammation, and help the remaining tumor evade immune attack.

We have spent decades counting the cells we destroyed and treating what their destruction left behind as somebody else’s concern. It may be part of the disease.

Five jobs, not one

If all of that is right, then an approach aimed seriously at relapse has more than one job.

It has to deliver damage the cancer cannot repair or survive. It has to reach the stem-like population specifically, not just the bulk. It has to clean up the debris so the wreckage does not rebuild what you dismantled. It has to work against the four survival strategies. And it has to do all of that on a schedule where the pieces help rather than cancel each other.

What follows is the reasoning behind an approach built around those jobs. This mechanistic rationale draws on published laboratory and animal research.

The strike

The central agent is an ozonated oil with very high ozonide content. Ozone has been tried against cancer before, as a gas and dissolved in water, with real but brief effects, because ozone is volatile and cells are wrapped in a fatty membrane that gas and water cross poorly. Carrying the oxidizing chemistry in an oil changes that. The oil gets inside.

Once there, it oxidizes mitochondrial membranes. The mitochondrion would normally trigger a damaged cell to shut itself down, and in cancer cells that machinery sits idle. Oxidizing it directly releases calcium into the cytoplasm and starts the shutdown sequence anyway, without requiring the p53 gene that so many tumors have lost. In lung and glioblastoma cell lines, high-ozonide preparations dropped viability below 10% within a day, while the lower-ozonide products sold commercially did not come close.

The researcher behind this work argues that it should reach the stem-like population specifically, on the reasoning that those cells survive treatment precisely because they carry the deepest antioxidant reserves, which is exactly what makes them vulnerable once an oxidative attack arrives and those reserves are the thing being attacked. I find that reasoning persuasive. I also have to tell you that his experiments did not sort for stem cell markers, so the claim is an inference rather than a demonstration.

Three things sharpen the strike. Piperlongumine, from long pepper, disables an enzyme that maintains the antioxidant reserve. Niclosamide, an old deworming drug, collapses the cell’s energy production and suppresses the switch that runs the antioxidant program. Omega-3 fatty acids incorporate into cell membranes over a period of weeks, making those membranes more readily oxidized, which may give the strike more to work with. They also lower the inflammatory signals that help tumors recruit immune-suppressing cells.

One point on timing comes from the ozonide research itself. The oil is strongly radiosensitizing, and in cell experiments the effect was largest when the oil was applied after radiation rather than before. In practice, the oil is taken daily rather than timed to individual sessions, so it is present throughout, but that finding still tells you something about how the two fit together. Radiation clears the bulk of a tumor and leaves an enriched stem-like population behind, which is exactly the population the oil targets.

Reaching the stem cells

The second approach to that population comes from an unexpected direction.

In a screen of over a thousand compounds, including many already approved by the FDA, the Bayer group found that PDE5 inhibitors reduced the stem-like fraction and sharply cut those cells’ ability to form new tumor spheres. Silencing the PDE5 gene directly produced the same result, which is a good sign that the effect is real and on target. The proposed mechanism is not killing at all. Raising one cellular messenger blocks the breakdown of another, which activates a signaling pathway that pushes these cells to differentiate into ordinary, non-stem tumor cells.

That is worth pausing on. Rather than trying to kill the hardest cells to kill, this coaxes them out of the state that makes them hard to kill, into a state where everything else already works.

Two honest caveats. The work was done in cell lines in flat culture, and the authors say plainly that this is a limited model for stem cells in a real tumor. And the specific molecules tested were not the PDE5 inhibitor most often used in clinical practice, though they all act on the same target.

That last point matters in practice, because PDE5 inhibitors are common prescription medications with decades of safety data behind them. They also do something else worth knowing. In randomized, placebo-controlled trials in head and neck cancer, a PDE5 inhibitor reduced two populations of immune-suppressing cells that tumors recruit to protect themselves, and increased the patient’s own T cells reactive against their tumor. That is human trial evidence, which is more than most of what I describe here can claim, and it’s why this class sits near the center of the approach rather than at its edge.

The acidity problem

Tumors turn their surroundings acidic, and that acidity does more damage than it first appears.

Below a certain pH, immune cells stop working properly. T cells become unresponsive, and laboratory work shows that this unresponsiveness reverses when acidity is buffered. In animal studies, neutralizing tumor acidity improved immunotherapy responses. Acidity also helps tumor cells invade surrounding tissue, drives the release of enzymes that break down the surrounding matrix, and appears to help maintain the stem-like population we have been discussing.

Raising the pH of the tumor neighborhood with an alkalinizing mineral blend sits upstream of everything else in this section. Clearing away immune-suppressing cells accomplishes less than it should if the immune cells that remain cannot function in the environment they are working in. Fix the environment first, and the rest has somewhere to act.

Two practical notes. The target here is the fluid immediately around the tumor rather than the blood, which your body buffers tightly and which should not shift. And progress is measurable at home with urine test strips, which makes this one of the few parts of this approach where you can actually see whether it is working. A plant-forward diet moves the same number in the same direction.

The cleanup

The debris problem is addressed with very small doses of resveratrol paired with very small amounts of copper. The chemistry is simple: resveratrol reduces copper; that reaction generates oxygen radicals that are absorbed and spread through the extracellular space, and those radicals break up chromatin particles before they reach living cells.

The doses are far below what you would find in an ordinary supplement, and the researchers found something counterintuitive. Activity increases as the copper is lowered relative to the resveratrol. Less works better, the opposite of how most people think about supplements, and this cannot be approximated by taking more of either.

In studies from the Tata Memorial Centre in India, this pairing reduced toxicity in patients receiving high-dose chemotherapy, and in a 2025 study of ten glioblastoma patients treated for under two weeks before surgery, the chromatin particles abundant in untreated tumor tissue were largely gone, proliferation markers fell, and several immune checkpoints and stem cell markers were reduced.

What is still missing

Of the five jobs, one currently has no good tool. Nothing in this approach meaningfully interferes with cancer cells’ DNA repair machinery. The candidates I have looked at each carry a problem serious enough to disqualify them: one impairs repair but drives up the drug efflux pumps as a side effect, one works but its main toxicity is suppressing the bone marrow in patients who often cannot afford that, and one may weaken the immune cells we are working to mobilize.

I’ve also stopped looking for a reason. The real tools for interfering with cancer DNA repair already exist, and they are cancer drugs called PARP inhibitors. For patients whose tumors carry a BRCA mutation or what is called homologous recombination deficiency, these are not experimental. They are approved, they work, and they belong in the hands of your oncologist rather than anywhere near a list of supplements or repurposed drugs. So for that group of patients, this job is not missing a tool at all. It is simply somebody else’s job, and the useful question is not what to add but whether your tumor has been tested for those markers. If it has not been, ask about it at your next appointment, because a positive result opens a door that nothing in this article comes close to matching.

There is some consolation, and I don’t want to oversell it. Because the stem-like cells are where radiation resistance largely lives, depleting them addresses the practical consequence of efficient repair without touching the repair machinery itself. That is a different mechanism arriving at an overlapping result, not a substitute for the real thing.

Where this leaves you

None of this is a shopping list, and that is the part I most want to land. What I have described is reasoning drawn from laboratory and animal work, and reasoning is how good hypotheses get built rather than how they get proven. The pieces also differ considerably in how much sits behind them. Randomized human trials have tested the effect of PDE5 inhibition on immune-suppressing cells. Several of the others rest on cell culture and mouse models and nothing more. And no one has ever tested this combination.

So the value of understanding these mechanisms isn’t that it tells you what to take. It gives you better questions to bring to the people directing your care. If this treatment stops working, do we have a sense of which mechanism is likely responsible? Is there something we could do about that in advance rather than after the fact? Has my tumor been tested for the markers that would open other doors? And for anything added alongside standard treatment, what is your view on the timing, since oxidative and antioxidant approaches can work against each other depending entirely on when each one is given?

That last question matters more than most people realize, and it’s why anything undertaken here belongs with a physician who knows your full history, is watching your bloodwork, and is talking with your oncology team rather than working around it. We are given bodies with remarkable repair systems already built into them. Good stewardship of them means neither neglecting what we can influence nor claiming more certainty than we have. Both errors cost patients, and in my experience the second one costs them more.

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This information is for educational purposes and does not constitute medical advice, diagnosis, or treatment. Integrative metabolic support and repurposed medications are intended to complement, not replace, care directed by your treating oncology team. No approach described here is presented as a cure for cancer, and individual results vary. Off-label prescribing means using a medication approved for one condition for another. It is legal and common in medical practice and is done with informed consent after discussing known risks. Always consult your physician before changing your care.