Hyperbaric oxygen therapy (HBOT) has been used for decades to help patients recover from injuries, wounds, and the side effects of cancer treatment. One of its most important roles is in healing radiation damage—soft tissue injuries that can develop months or even years after treatment. Patients with head and neck cancer, breast cancer, pelvic cancers, and others often benefit from HBOT to relieve pain, improve tissue healing, and restore quality of life.
But for years, some patients and providers have worried: Could HBOT make cancer grow faster? This concern comes from an old, flawed study published in the 1960s. Modern research has now shown that this fear is a myth. Not only does HBOT not fuel cancer, it may actually improve the effectiveness of radiation, chemotherapy, and immunotherapy while continuing to play a vital role in healing from treatment side effects.
Where Did the Fear Come From?
In 1966, a small case report suggested that women with cervical cancer who received HBOT with radiation had “more metastases than expected.” This study included only 25 patients, lacked a control group, and had no statistical analysis. Later research—including larger studies and even reassessment by the original authors—showed no increase in tumor spread or recurrence. Still, the initial report created a lingering fear that HBOT could be unsafe for people with cancer (Johnson & Lauchlan, Am J Obstet Gynecol, 1966).
What Do Laboratory and Animal Studies Show?
Extensive laboratory studies have tested the effects of HBOT on cancer cells. In prostate cancer, melanoma, glioma, and breast cancer models, HBOT exposure did not accelerate growth. In many cases, it actually slowed tumor proliferation or made cancer cells more sensitive to treatment (Kalns et al., J Appl Physiol, 1998; Feldmeier et al., Undersea Hyperb Med, 2003; Moen & Stuhr, Target Oncol, 2012).
Animal studies tell the same story. The majority show no effect of HBOT on tumor growth, and several demonstrate tumor inhibition. A 2024 meta-analysis of mouse cancer models confirmed these findings, showing that HBOT prolonged survival compared to controls. Importantly, when combined with chemotherapy or radiation, HBOT significantly improved survival even further (Klement et al., Oncologie, 2024).
Why Oxygen Might Help, Not Hurt
Cancer cells thrive in low-oxygen (hypoxic) environments, which drive them to spread and resist treatment. HBOT delivers 100% oxygen at increased pressure, which changes the tumor environment in ways that counteract these survival mechanisms.
Research has shown that HBOT reduces hypoxia and lowers levels of HIF-1α, a protein that helps tumors grow new blood vessels. It also decreases resistance proteins that protect tumors from chemotherapy and improves blood vessel structure, making it easier for treatments to reach cancer cells. In addition, HBOT boosts the immune system’s ability to recognize and attack cancer cells, enhancing responses to immunotherapies (Wang et al., Front Oncol, 2023; Stępień et al., Med Oncol, 2016).
What About Human Studies?
Human studies across many cancers have consistently shown that HBOT does not increase recurrence or spread. In fact, some trials demonstrated improved local tumor control when HBOT was combined with radiation. In cervical and head and neck cancers, HBOT was found to be safe and in some cases enhanced treatment outcomes (Daruwalla & Christophi, World J Surg, 2006).
One of the most recent and important clinical studies was the HONEY trial, published in JAMA Oncology, which evaluated HBOT in breast cancer survivors experiencing late radiation side effects. HBOT significantly improved pain and reduced fibrosis compared to controls, showing meaningful benefits in quality of life. Importantly, there was no evidence of increased cancer recurrence or progression in patients receiving HBOT (Meier et al., Breast, 2023).
HBOT is also widely used for radiation side effects such as jawbone damage (osteoradionecrosis), breast fibrosis, bladder irritation, and soft tissue pain. Systematic reviews confirm that HBOT improves these conditions without increasing the risk of cancer returning. Ongoing clinical trials are now exploring how HBOT can be used more intentionally as a partner to radiation and chemotherapy in cancers of the brain and head and neck (ClinicalTrials.gov, NCT03843671).
The Bottom Line
The fear that HBOT “feeds cancer” was based on a single, flawed study from 1966. Decades of evidence have now proven otherwise. Laboratory studies, animal experiments, and human clinical trials all show that HBOT is safe for people with cancer. In many cases, it may actually help treatments work better. At the same time, HBOT plays an important role in helping survivors heal from the side effects of radiation and regain quality of life.
The next step will be randomized clinical trials designed specifically to test whether HBOT can be used prophylactically in cancer care—for example, to prevent radiation damage or enhance the effects of therapy—while confirming through randomization that there is no increase in cancer progression risk. Based on the extensive data so far, there is no reason to believe HBOT promotes tumor growth, and patients should feel reassured about its safety.
References
- Johnson RJ, Lauchlan SC. Hyperbaric oxygen as an adjunct to radiation therapy in carcinoma of the cervix. Am J Obstet Gynecol. 1966.
- Feldmeier JJ, Carl U, Hartmann K, Sminia P. Hyperbaric oxygen: Does it promote growth or recurrence of malignancy? Undersea Hyperb Med. 2003;30(1):1–18.
- Kalns J, et al. Hyperbaric oxygen exposure and growth of prostate cancer xenografts. J Appl Physiol. 1998;85(2):795–8.
- Moen I, Stuhr LE. Hyperbaric oxygen therapy and cancer—a review. Target Oncol. 2012;7(4):233–42.
- Klement RJ, Eckert JM, Sweeney RA. Anti-cancer effects of hyperbaric oxygen therapy in mice: a meta-analysis. Oncologie. 2024;26(6):941–55.
- Wang P, Wang XY, Man CF, Gong DD, Fan Y. Advances in hyperbaric oxygen to promote immunotherapy through modulation of the tumor microenvironment. Front Oncol. 2023;13:1200619.
- Stępień K, et al. Hyperbaric oxygen as adjunctive therapy in treatment of malignancies, including brain tumours. Med Oncol. 2016;33(9):101.
- Daruwalla J, Christophi C. Hyperbaric oxygen therapy for malignancy: A review. World J Surg. 2006;30(12):2112–31.
- Meier EL, et al. Hyperbaric oxygen therapy for local late radiation toxicity in breast cancer patients: systematic review. Breast. 2023.
- ClinicalTrials.gov. NCT03843671. Hyperbaric radiation sensitization of head and neck and brain tumors.