Lack of resources to complete the study

Background: Radiotherapy is a common treatment for many malignancies. Radiation-related complications developing months or years after radiation treatment are known as late radiation tissue injury (LRTI) and are estimated to effect 5%-15% of all long-term survivors who have received radiation.

Hyperbaric oxygen therapy (HBOT) is a well established treatment of LRTI. Most of the studies evaluating effect of HBOT on LRTI are focused on survival, resolution of tissue damage and improvement in LENT-SOMA scale. Very few studies have addressed effect of HBOT on pain in LTRI. Krahn and colleagues were the first to report the analgesic effect of HBOT in 3 cases of refractory pain in oncological patients with radiation soft tissue injury. Other studies showed significant improvement in pain intensity in patients with breast cancer and pelvic malignancies treated with HBOT for LTRI. In patients that had developed radiation- induced brachial plexopathy, HBOT elicited an increase in warm pain thresholds and a reduction in lymphoedema. A prospective case study of 16 patients with gynecological cancer found no changes with respect to pain and depression outcomes. A trial in patients with radiation induced proctopathy showed that 75% of patients with rectal pain had some improvement, although none experienced a complete resolution of pain symptoms.

There are several mechanisms by which HBOT may elicit analgesic effects. There is a growing body of evidence that HBOT's analgesic effect related to nitric oxide metabolism and endogenous opioid secretion. Furthermore, the inhibition of tumor necrosis factor alph (TNF-α), the production of substance P, and the modulation of serotonergic pathways have all demonstrated a modification in the pain response following HBOT. In animal studies HBOT decreased allodynia and hyperalgesia in different models of neuropathic and inflammatory pain. The long lasting antinociceptive effect of HBOT was found to be dose-dependent in non-injured tissues.

In human studies, HBOT decreased pain and edema and improved function in patients suffering from the complex regional pain syndrome, and improved pain scores and range of motion in patients with idiopathic femoral head necrosis. Women suffering from interstitial cystitis demonstrated a reduction in pelvic pain following weeks and months of HBOT treatment. In patients suffering from idiopathic trigeminal neuralgia HBOT produced a rapid reduction in symptoms and these effects were lasting for 6 months following treatment. HBOT was also found to be an effective treatment for cluster headaches and migraines and alleviated muscle and bone pains in patients with myofascial syndrome, fibromyalgia, and biphosphonate-related osteonecrosis of the jaw.

Based on the evidence presented above and HBOT's known analgesic effect in many conditions, the investigators designed this study with the objective to evaluate if HBOT reduces pain, improves depression and impacts on patients quality of life in patients suffering from late radiation tissue injury.

Study Design: Prospective observational study (n=300). Patients that have had radiation therapy for malignancy, developed late radiation injury and suffer from chronic pain.

Inclusion Criteria:

• Patients who had radiation therapy, developed late radiation tissue injury and are eligible for hyperbaric oxygen therapy.
• Pain ≥ 5 in any anatomic site with duration > 3 months

Exclusion Criteria:

• Patient refusal
• Patient inability to answer the questionnaires

All patients undergoing hyperbaric oxygen therapy for delayed radiation tissue injury in the Hyperbaric Unit.