Unraveling the Science: Can Ozone Therapy Aid Cancer Treatment?

Ozone therapy is sometimes discussed in the context of cancer care. This page sets out what the published research actually shows, what kind of studies it comes from, and where the evidence stops. It is not a claim that ozone treats cancer, and nothing here is a substitute for oncological care.

Background: why ozone has been investigated in oncology

Tumour tissue is often poorly oxygenated, and low oxygen availability is associated with tumour progression. That observation has prompted researchers to ask whether therapies that alter oxygenation or introduce controlled oxidative stress might have a role alongside conventional treatment. Ozone has been examined on those grounds, mostly as a possible adjunct to radiotherapy and chemotherapy rather than as a treatment in its own right.

For general background on the therapy itself, see our ozone therapy hub.

The clinical evidence: one non-randomised study in 115 patients

The most substantial human study in this area is Izzotti and colleagues, published in Cancers in 2022. A total of 115 patients with brain, lung, pancreatic, colon and skin cancers took high-ozonide ozonated oil orally as a complementary therapy alongside standard chemotherapy and radiotherapy regimens, with follow-up of up to four years. The authors reported an increase in survival rate and a reduction in relapses compared with standard treatment alone.

The design matters as much as the result. This was not a randomised controlled trial and it was not blinded, so patients were not allocated by chance and neither they nor the researchers were kept unaware of who received what. That leaves the findings open to selection effects and expectation effects in a way a randomised trial would guard against. The paper also reports its own sample composition inconsistently between the abstract and the journal's peer review record. It is a genuine and interesting clinical signal; it is not confirmation.

The preclinical evidence: animal and laboratory work

Most of the remaining evidence comes from animals and from cells in culture, and it should be read as mechanism rather than outcome.

Two 2008 studies in mice, described in a 2018 review by Clavo and colleagues, implanted Ehrlich ascitic tumour and sarcoma 37 cells and then treated the animals with ozone by rectal insufflation over twelve sessions. A significant reduction in the number of lung metastases was observed, with fewer tumour cells per mouse at higher ozone concentrations.

In a rat model, ozone combined with radiotherapy was studied in tongue cancer, and separately, an in vitro study examined ozone's effect on a metastatic breast cancer cell line. That second study was carried out on cells in a dish, not in a living animal, which limits what can be inferred from it.

The animal evidence is not uniformly favourable, and it would be misleading to present only one side of it. Work on ozone as an air pollutant has found that whether ozone enhances or inhibits lung tumour development in mice depends on the experimental design, and that ozone exposure can increase lung colonisation by cancer cells in some conditions. Route, dose and timing appear to change the direction of the effect, not just its size.

Alongside radiotherapy and chemotherapy

The most consistent theme in this literature is not ozone acting on tumours directly, but ozone used alongside conventional treatment, with two possible roles: improving tumour oxygenation to make radiotherapy more effective, and reducing the side effects of treatment. A study in advanced head and neck tumours examined ozone as an adjuvant on that basis.

Related to this, ozone has been studied for wound healing in chronic wounds, which is relevant where surgery precedes radiotherapy or chemotherapy and delayed healing would postpone the next stage of treatment.

Limitations of the evidence base

Taken as a whole, the picture is early. There is one non-randomised human study of reasonable size, a set of small animal studies whose results vary with experimental design, and laboratory work on cells. Large randomised controlled trials in people with cancer have not been done. Proponents often attribute that to funding difficulties, since ozone cannot be patented, and there is something to that argument, but the absence of those trials is a fact about the evidence regardless of its cause.

Reported findings also cluster around two quite different claims that are easy to conflate: effects on the cancer itself, and effects on treatment tolerability and quality of life. The second is better supported than the first.

If you are living with cancer

Ozone therapy is not a cancer treatment and is not an approved or registered medical treatment in New Zealand. Nothing on this page should be used to delay, replace or alter oncological care.

If the research here interests you, the constructive step is to take it to your oncology team. The studies above are linked in full so you can share them and have a properly informed conversation, including about interactions with the treatment you are already receiving. Decisions about complementary approaches during cancer treatment belong with the clinicians managing your care.

If you have questions about ozone therapy in general, you are welcome to contact us - though for anything relating to your own diagnosis or treatment, your medical team is the right place to start.