Hyperbaric Oxygen Therapy (HBOT) involves breathing 100% oxygen within a sealed chamber where the atmospheric pressure is increased to two or three times the normal level. This process forces a significantly higher amount of oxygen to dissolve into the plasma, allowing it to reach tissues with reduced blood flow. While HBOT is standard for conditions like decompression sickness and non-healing wounds, its application in cancer care is complex. It is important to distinguish between its established role in managing treatment complications and its experimental use against the tumor itself.
Managing Treatment Side Effects
The most established use of HBOT in oncology is treating complications that arise long after a patient has completed radiation therapy. Radiation, while effective against cancer cells, can damage the small blood vessels in surrounding healthy tissues, leading to delayed radiation injury. This damage results in chronic, poorly oxygenated tissue that struggles to heal, sometimes manifesting months or years post-treatment.
One common and severe form of this damage is osteoradionecrosis, the death of bone tissue, frequently occurring in the jawbone after head and neck radiation. HBOT helps by directly addressing the lack of oxygen in the damaged area. The pressurized oxygen stimulates angiogenesis, the formation of new blood vessels, which restores blood flow and delivers necessary nutrients to the tissue.
Beyond promoting new blood vessel growth, high oxygen levels also stimulate fibroblasts, cells responsible for producing collagen. This enhanced collagen deposition strengthens the tissue, improving its quality and capacity for long-term healing. HBOT is also commonly used for other delayed radiation injuries, such as radiation cystitis (bladder inflammation) and proctitis (rectal inflammation). It acts as an effective adjunct to surgical or medical management, helping refractory wounds in irradiated tissue close.
Theoretical Impact on Tumor Progression
The question of whether HBOT can directly affect a tumor centers on tumor hypoxia, where areas within a solid tumor have low oxygen levels. This hypoxic environment makes cancer cells more resistant to both radiation therapy and certain chemotherapy agents. The theory is that by temporarily increasing the oxygen concentration in the bloodstream, HBOT could overcome this hypoxia, thereby sensitizing the tumor cells to conventional treatments.
This process, known as radiosensitization or chemosensitization, aims to exploit the fact that oxygen is necessary for radiation to cause maximum damage to the cancer cell’s DNA. Studies show that HBOT can significantly increase the tissue oxygen pressure within tumors. The goal is to time the HBOT session immediately before or during the administration of radiation or chemotherapy to maximize the therapeutic effect.
This therapeutic hypothesis was accompanied by a long-standing controversy: the fear that HBOT might promote tumor growth or metastasis. Because high oxygen levels stimulate wound healing and angiogenesis in healthy tissue, there was concern that the same effect could accelerate malignant progression. Extensive research, including systematic reviews, has largely mitigated this concern, concluding that HBOT does not appear to promote cancer growth or recurrence. The mechanisms governing angiogenesis in a tumor differ from those in a healing wound, and studies have found HBOT does not enhance tumor vascularization or increase metastasis.
Clinical Evidence and Safety Considerations
Current clinical evidence supports the use of HBOT primarily as an adjunctive therapy, meaning it is used in addition to standard cancer treatments like surgery, radiation, and chemotherapy. Randomized controlled trials examining HBOT as a radiosensitizer have shown mixed results. However, some evidence suggests it may improve local tumor control and reduce recurrence in specific cancers, such as certain head and neck malignancies. HBOT is not a standalone cure for cancer, and no evidence supports its use as a primary monotherapy.
Safety is paramount, and clinicians must consider several contraindications and risks before recommending HBOT to a cancer patient. Absolute contraindications include untreated pneumothorax and certain chemotherapy drugs that interact negatively with high oxygen levels. HBOT itself carries a low risk of complications, most commonly ear barotrauma, which is pressure-related discomfort or injury to the middle ear.
For cancer patients, the safety profile of HBOT is generally favorable when administered under appropriate medical supervision. Multiple studies have found no significant correlation between HBOT sessions and an increased risk of tumor progression, recurrence, or metastasis in patients with solid tumors. Decisions to pursue HBOT require careful consultation with the patient’s oncologist and a hyperbaric medicine specialist. Most clinical protocols utilize pressures between 2.0 and 2.5 atmospheres absolute (ATA) for sessions lasting 90 to 120 minutes.