Delayed Radiation Injury to Soft Tissues

• Soft Tissue Radionecrosis
• Complications from Radiation Therapy

• Delayed radiation injuries are typically seen after a latent period of six months or more and may develop many years after the radiation exposure. These injuries can cause significant debilitation to patients. Often, delayed injuries are precipitated by an additional tissue insult such as surgery within the radiation field.

• Hyperbaric oxygen treatment allows more oxygen to reach these radiation damaged areas. A series of hyperbaric oxygen treatments can help to stimulate new blood vessels to grow. This gives the body the opportunity to heal and significantly improve, if not totally relieve patients of their presenting symptoms.
• Hyperbaric oxygen treatment stimulates angiogenesis – neo-vascularisation – Improves post operative healing / surgical outcomes in the area of previous radiation, including increased success of skin grafting or flap.
• Hyperbaric oxygen can mobilize & stimulate an increase of stem cells by increasing nitric oxygen in normal tissues. Similar effect in irradiated tissues is likely.
• Hyperbaric oxygen also increases the ability of infection-fighting white blood cells to kill harmful bacteria and accelerate healing.

Hyperbaric oxygen therapy is usually used as an adjunct to additional care the patient is receiving. Additional treatments may also include antibiotic therapy, nutritional support, and surgical procedures, if indicated.

The Known Studies Demonstrating Effects Of Hyperbaric Oxygen On Irradiated Tissues

Because a consistent cause and manifestation of radiation injury is vascular obliteration and stromal fibrosis, the known impact of hyperbaric oxygen in stimulating angiogenesis is an obvious and important mechanism whereby hyperbaric oxygen is effective in radiation injury.

• Marx has demonstrated the enhanced vascularity and cellularity in heavily irradiated tissues after hyperbaric oxygen therapy by comparing histologic specimens from patients pre- and post- hyperbaric oxygen.
• Marx has also demonstrated the serial improvement in transcutaneous oxygen measurements of patients receiving hyperbaric oxygen as an indirect measure of vascular improvement.
• Marx et al in an animal model have shown increased vascular density in rabbit mandibles after exposure to hyperbaric oxygen.
• Feldmeier and his colleagues in a murine model of radiation damage to the small bowel have shown that prophylactic hyperbaric oxygen can reduce the degree and mechanical effects of fibrosis by being applied prior to the manifestation of radiation injury. Assays of the murine bowel for collagen content and compliance included a mechanical stretch assay as well as quantitative histologic assays of fibrosis in the tunica media of the animal bowel.
• The hyperbaric study group headed up by Dr. Thom at the University of Pennsylvania has recently published two studies demonstrating that hyperbaric oxygen can mobilize stem cells by increasing nitric oxygen. This mechanism has not as yet been proven to have a major impact on irradiated tissues.
• Significant reduction in the woody fibrosis of soft tissues seen frequently in head and neck cancer patients after radiation with a course of hyperbaric oxygen intended to treat mandibular necrosis.

Hyperbaric oxygen has been applied as a therapy for delayed radiation injury for more than 30 years.

Prophylactic interventions such as hyperbaric oxygen could be applied during the latent period but before the manifestation of the chronic radiation injury which could be prevented or at least reduced in its severity.

Radiation damage can occur anywhere in the body that radiotherapy has been used to treat cancer.

• Radiation to the urinary bladder can cause pain, incontinence and bleeding, this is called radiation hemorrhagic cystitis.
• Radiation proctitis or enteritis can occur when there is radiation to the area of the lower GI tract. This can cause pain, incontinence, spasms, diarrhea, and bleeding.
• Additional radiation injuries in this area can lead to fistula formation or wounds directly connected to the bowel. Delayed radiation injury to other soft tissue locations can cause wounds, pain and neurolgical deficits.
• Hyperbaric oxygen also has a frequent application in the prevention of mandibular osteoradionecrosis when dental extractions are required from heavily irradiated mandibles.