• SOMA (Subjective, Objective, Management, Analytic) scale used to determine late effects to normal tissue (LENT) score [ Time Frame: pre-treatment, post-treatment (HBO and placebo) and at follow ups at 3 months, 6 months, and 1 year through 5 years ] [ Designated as safety issue: No ]
  

• Clinical assessment using one of the following criteria: [ Time Frame: post-treatment (HBO and placebo) and at follow ups at 3 months, 6 months, and 1 year through 5 years ] [ Designated as safety issue: No ]
  
• Healed [ Time Frame: post-treatment (HBO and placebo) and at follow ups at 3 months, 6 months, and 1 year through 5 years ] [ Designated as safety issue: No ]
  
• Modestly improved (< 50% lesion resolution) [ Time Frame: post-treatment (HBO and placebo) and at follow ups at 3 months, 6 months, and 1 year through 5 years ] [ Designated as safety issue: No ]
  
• Not improved [ Time Frame: post-treatment (HBO and placebo) and at follow ups at 3 months, 6 months, and 1 year through 5 years ] [ Designated as safety issue: No ]
  
• Other (e.g. lesion recurrence, lesion size progression) [ Time Frame: post-treatment (HBO and placebo) and at follow ups at 3 months, 6 months, and 1 year through 5 years ] [ Designated as safety issue: No ]
  
• Significant Improvement (>50% lesion resolution) [ Time Frame: post-treatment (HBO and placebo) and at follow ups at 3 months, 6 months, and 1 year through 5 years ] [ Designated as safety issue: No ]
  

Radiation therapy is a key component of the control and eradication of malignant disease. Adequate tumoricidal doses may, however, result in damage to surrounding healthy tissue. Therapeutic radiation injuries to non-target tissues can be divided into acute, sub-acute, and delayed complications. Acute injuries are considered a direct cellular toxicity, self-limiting, and in most cases successfully managed symptomatically. Sub-acute injuries are typically identifiable in only a few organ systems, e.g., radiation pneumonitis. These, too, are generally limited but occasionally evolve to late complications. Late changes occur several months to many years after completing radiotherapy.

The etiology of radiation's late effects to normal tissue (LENT) varies somewhat between organ systems. Its hallmark, however, is one of culminating in an obliterative endarteritis, and local hypoxia.

The incidence of LENT is related to both total radiation exposure and the length of time a patient is out from completing radiotherapy. The higher the dose, the longer the interval from exposure, the greater the risk. In many cases, resulting radionecrotic lesions seriously impair form and function, and require extensive surgical correction or repair. Such surgery is fraught with complications, hence the inclusion of a "prophylactic" hyperbaric oxygen arm. A disturbing degree of mortality further complicates the development of LENT.

Hyperbaric oxygen has been utilized in the treatment of radiation tissue injury for several decades. Most of the supportive basic science and clinical evidence stems from the management of mandibular osteoradionecrosis. More recently, the use of hyperbaric oxygen has been extended to other anatomic sites. This expanded use is based, in large part, on a presumed common underlying pathophysiology of LENT, regardless of its anatomic location. Supportive clinical evidence for these other sites is limited, however, and in need of a greater degree of scientific scrutiny.