Hyperbaric oxygenation for tumour sensitisation to radiotherapy: a systematic review of randomised controlled trials.

BACKGROUND: Radiotherapy is a well-established treatment for some solid tumours. Hyperbaric oxygenation (HBO) may improve radiotherapeutic killing of hypoxic cancer cells, so the simultaneous administration of radiotherapy and HBO may reduce mortality and tumour recurrence. METHODS: We performed a systematic search of the literature in September 2007 for randomised controlled trials, and made pooled analyses of pre-determined clinical outcomes. RESULTS: Nineteen trials contributed to this review (2286 patients). There was a reduction in mortality for head and neck cancers at one and five years after therapy (at five years RR 0.82, P=0.03, NNT=5), and improved local tumour control at three months (RR 0.58, P=0.006, NNT=7). Any advantage is achieved at the cost of an increased rate of both severe radiation tissue injury (RR 2.35, P<0.0001, NNH=8) and the chance of seizures during therapy (RR 6.76, P=0.03, NNH=22). CONCLUSIONS: There is some evidence that HBO improves local tumour control and mortality for cancers of the head and neck, and local tumour recurrence in cancers of the uterine cervix. These benefits may only occur with unusual fractionation schemes. HBO is associated with significant adverse effects including oxygen toxic seizures and severe radiation tissue injury. The methodological and reporting inadequacies of the studies included in this review demand a cautious interpretation. More research is needed for head, neck and uterine cervical cancer, but is probably not justified for bladder cancer. There is little evidence available concerning malignancies at other sites.

Hyperbaric oxygenation for tumour sensitisation to radiotherapy.

BACKGROUND: Cancer is common and radiotherapy is one well-established treatment for some solid tumours. HBO may improve the ability of radiotherapy to kill hypoxic cancer cells, so the administration of radiotherapy while breathing HBO may result in a reduction in mortality and tumour recurrence. OBJECTIVES: To assess the benefits and harms of radiotherapy while breathing HBO. SEARCH STRATEGY: In November 2004 we searched The Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library Issue 3), MEDLINE, EMBASE , CINAHL, DORCTHIM and reference lists of articles. Relevant journals were handsearched. SELECTION CRITERIA: Randomised and quasi-randomised studies comparing the outcome of malignant tumours following radiation therapy while breathing HBO versus air (with or without sham therapy). DATA COLLECTION AND ANALYSIS: Three reviewers independently evaluated the quality of the relevant trials using the method of Schulz (Schulz 1995) and extracted the data from the included trials. MAIN RESULTS: Nineteen trials contributed to this review (2286 patients: 1103 allocated to HBO and 1153 control). With HBO, there was a reduction in mortality for head and neck cancers at both one year and five years after therapy (Relative risk (RR) 0.83, P = 0.03, number needed to treat (NNT) = 11 and RR 0.82, P = 0.03, NNT = 5 respectively), as well as improved local tumour control at three months (RR with HBOT 0.58, P = 0.006, NNT = 7). The effect of HBO varied with different fractionation schemes. Local tumour recurrence was less likely with HBO at one year (head and neck, RR 0.66, P < 0.0001, NNT = 5), two years (uterine cervix RR 0.60, P = 0.04, NNT = 5) and five years (head and neck (RR 0.77, P = 0.01). Any advantage is achieved at the cost of some adverse effects. There was a significant increase in the rate of both severe radiation tissue injury (RR 2.35, P < 0.0001, (number needed to harm (NNH) = 8) and the chance of seizures during therapy (RR 6.76, P = 0.03, NNH 22) with HBO. AUTHORS' CONCLUSIONS: There is some evidence that HBO improves local tumour control and mortality for cancers of the head and neck, and local tumour recurrence in cancers of the head and neck, and uterine cervix. These benefits may only occur with unusual fractionation schemes. HBO is associated with significant adverse effects including oxygen toxic seizures and severe tissue radiation injury. The methodological and reporting inadequacies of the primary studies included in this review demand a cautious interpretation. More research is needed for head and neck cancer, but is probably not justified for bladder cancer. There is little evidence available concerning malignancies at other anatomical sites on which to base a recommendation.

Hyperbaric oxygen therapy for late radiation tissue injury.

BACKGROUND: Cancer is a significant global health problem. Radiotherapy is a treatment for many cancers and about 50% of patients having radiotherapy with be long-term survivors. Some will experience LRTI developing months or years later. HBOT has been suggested for LRTI based upon the ability to improve the blood supply to these tissues. It is postulated that HBOT may result in both healing of tissues and the prevention of problems following surgery. OBJECTIVES: To assess the benefits and harms of HBOT for treating or preventing LRTI. SEARCH STRATEGY: We searched The Cochrane Central Register of Controlled Trials (CENTRAL) Issue 3, 2004, MEDLINE, EMBASE, CINAHL and DORCTHIM (hyperbaric RCT register) in September 2004. SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing the effect of HBOT versus no HBOT on LRTI prevention or healing. DATA COLLECTION AND ANALYSIS: Three reviewers independently evaluated the quality of the relevant trials using the guidelines of the Cochrane Handbook Clarke 2003) and extracted the data from the included trials. MAIN RESULTS: Six trials contributed to this review (447 participants). For pooled analyses, investigation of heterogeneity suggested important variability between trials. From single studies there was a significantly improved chance of healing following HBOT for radiation proctitis (relative risk (RR) 2.7, 95% confidence Interval (CI) 1.2 to 6.0, P = 0.02, numbers needed to treat (NNT) = 3), and following both surgical flaps (RR 8.7, 95% CI 2.7 to 27.5, P = 0.0002, NNT = 4) and hemimandibulectomy (RR 1.4, 95% CI 1.1 to 1.8, P = 0.001, NNT = 5). There was also a significantly improved probability of healing irradiated tooth sockets following dental extraction (RR 1.4, 95% CI 1.1 to 1.7, P = 0.009, NNT = 4). There was no evidence of benefit in clinical outcomes with established radiation injury to neural tissue, and no data reported on the use of HBOT to treat other manifestations of LRTI. These trials did not report adverse effects. AUTHORS' CONCLUSIONS: These small trials suggest that for people with LRTI affecting tissues of the head, neck, anus and rectum, HBOT is associated with improved outcome. HBOT also appears to reduce the chance of osteoradionecrosis following tooth extraction in an irradiated field. There was no such evidence of any important clinical effect on neurological tissues. The application of HBOT to selected patients and tissues may be justified. Further research is required to establish the optimum patient selection and timing of any therapy. An economic evaluation should be also be undertaken. There is no useful information from this review regarding the efficacy or effectiveness of HBOT for other tissues.

Hyperbaric oxygen for delayed radiation injuries.

Hyperbaric oxygen has shown consistent benefit in treating patients with delayed radiation injury. It has also had success in preventing radiation injury in some instances. Additional study in identifying patients at risk for injury and delivering hyperbaric oxygen with prophylactic intent to prevent these injuries appears to be promising. Additional approaches to applying hyperbaric oxygen as a radiosensitizer also deserve further study. No convincing evidence exists to support concerns that hyperbaric oxygen enhances or stimulates malignant growth.

Hyperbaric oxygen: does it promote growth or recurrence of malignancy?

It has been a concern that a therapeutic modality recommended as an adjunct to healing and administered to promote proliferation of fibroblasts, epithelial cells and blood vessels in a wound could also lead to proliferation of malignant cells and angiogenesis in a malignant tumor. The first reported concern that hyperbaric oxygen (HBO2) might have cancer growth enhancing effects appeared in a paper by Johnson and Lauchlan in 1966. In a series of patients treated with HBO2 radiosensitization, they reported a more frequent than expected incidence of metastases and an unusual pattern of metastases. The published literature from clinical reports, animal studies and cell culture studies are reviewed. Putative mechanisms whereby HBO2 could have carcinogenic effects are discussed. The processes of angiogenesis in wound healing and in cancer growth are compared and contrasted. In vitro, in vivo and clinical studies strongly suggest no more than a neutral effect of HBO2 on tumor growth. In fact some studies suggest a negative impact of HBO2 on malignant progression or formation. For angiogenesis, similarities in wound healing and cancer are striking but significant differences are found including the relative importance of angiogenic factors and the process of cessation of angiogenesis. Tumors that grow in hypoxic environments are more prone to metastases and more lethal to the patient. They are also more likely to mutate toward resistant genotypes. Discussion of postulated mechanisms of carcinogenesis including free radical and immunosuppressive effects points out why they are not likely to enhance or cause cancer growth or initiation. In conclusion, the published literature on tumor angiogenesis mechanisms and other possible mechanisms of cancer causation or accelerated growth provides little basis for HBO2 to enhance malignant growth or metastases. A history of malignancy should not be considered a contraindication for HBO2 therapy.

A systematic review of the literature reporting the application of hyperbaric oxygen prevention and treatment of delayed radiation injuries: an evidence based approach.

The treatment of delayed radiation injuries (soft tissue and bony radiation necrosis) is one of thirteen conditions approved by the Hyperbaric Oxygen Therapy Committee of the Undersea and Hyperbaric Medical Society as appropriate indications for hyperbaric oxygen (HBO2). This paper provides a systematic review of the literature reporting the results of HBO2 therapy in the treatment and/or prophylaxis of delayed radiation injury. Since the introduction of the concept of evidence based medicine, the medical community in general has set out to apply more critical and stringent standards in evaluating published support for therapeutic interventions. Evidence based medicine is designed to discover the best evidence available and apply it in daily practice for treatment of the individual patient. The preferred level of evidence is the randomized controlled trial, however, other evidence has merit as well. In this review, seventy-four publications are represented reporting results of applying HBO2 in the treatment or prevention of radiation injuries. These are appraised in an evidence-based fashion by applying three established systems of evaluation. All but seven of these publications report a positive result when HBO2 is delivered as treatment for or prevention of delayed radiation injury. These results are particularly impressive in the context of alternative interventions. Without HBO2, treatment often requires radical surgical intervention, which is likely to result in complications. Other alternatives including drug therapies are rarely reported, and for the most part have not been the subject of randomized controlled trials. Based on this review, HBO2 is recommended for delayed radiation injuries for soft tissue and bony injuries of most sites. Of note, an increasing body of evidence supports HBO2 for radiation-induced necrosis of the brain. For other radiation-induced neurological injuries, additional study is required before recommendations for routine hyperbaric therapy can be made.

Hyperbaric oxygen therapy for late sequelae in women receiving radiation after breast-conserving surgery.

PURPOSE: Persisting symptomatology after breast-conserving surgery and radiation is frequently reported. In most cases, symptoms in the breast resolve without further treatment. In some instances, however, pain, erythema, and edema can persist for years and can impact the patient's quality of life. Hyperbaric oxygen therapy was shown to be effective as treatment for late radiation sequelae. The objective of this study was to assess the efficacy of hyperbaric oxygen therapy in symptomatic patients after breast cancer treatment. PATIENTS AND METHODS: Forty-four patients with persisting symptomatology after breast-conservation therapy were prospectively observed. Thirty-two women received hyperbaric oxygen therapy in a multiplace chamber for a median of 25 sessions (range, 7-60). One hundred percent oxygen was delivered at 240 kPa for 90-min sessions, 5 times per week. Twelve control patients received no further treatment. Changes throughout the irradiated breast tissue were scored prior to and after hyperbaric oxygen therapy using modified LENT-SOMA criteria. RESULTS: Hyperbaric oxygen therapy patients showed a significant reduction of pain, edema, and erythema scores as compared to untreated controls (p < 0.001). Fibrosis and telangiectasia, however, were not significantly affected by hyperbaric oxygen therapy. Seven of 32 women were free of symptoms after hyperbaric oxygen therapy, whereas all 12 patients in the control group had persisting complaints. CONCLUSIONS: Hyperbaric oxygen therapy should be considered as a treatment option for patients with persisting symptomatology following breast-conserving therapy.

Hyperbaric oxygen in the treatment of delayed radiation injuries of the extremities.

Hyperbaric oxygen (HBO2) is used as an adjunct in the treatment of radiation injury at many sites, including the mandible, larynx, chest wall, bladder, and rectum. In these disorders, HBO2 is effective in stimulating neovascularization and reducing fibrosis. No previous publications report the application of HBO2 to radiation injuries of the extremities. From 1979 until 1997, 17 patients were treated at the Southwest Texas Methodist and Nix Hospitals for nonhealing necrotic wounds of the extremities within previously irradiated fields. All but one wound involved a lower extremity. Most of the patients had been irradiated for soft tissue sarcomas or skin cancers. The rest were irradiated for a variety of malignancies. HBO2 was delivered in a multiplace chamber at 2.4 atm abs daily for 90 min of 100% oxygen at pressure. This report is a retrospective, uncontrolled review of these patients. Eleven patients (65%) healed completely whereas five (29%) failed to heal and one (6%) was lost to follow-up. Three (60%) of those who failed were found to have local or distant recurrence of their tumor early in their course of hyperbaric treatment and were discontinued from therapy at that time. When last seen in the clinic, the wound of the patient who was lost to follow-up was improved but not completely healed. Four of those who failed (including the two with local tumor recurrence) required amputation. If we exclude those with active cancer and the patient lost to follow-up, the success rate was 11 of 13 or 85%. HBO2 was applied successfully with complete wound healing and the avoidance of amputation in a majority of these patients. The consequences of failure in patients suffering from radiation necrosis of the extremities (some complicated by the presence of tumor) are significant, with 80% of the five failures requiring amputation. In radiation injuries of the extremities as in delayed radiation injury at other sites, HBO2 is a useful adjunct and should be part of the overall management.

Histologic morphometry confirms a prophylactic effect for hyperbaric oxygen in the prevention of delayed radiation enteropathy.

In a previous publication (Feldmeier et al., Radiother Oncol 1995; 35:138-144) we reported our success in preventing delayed radiation enteropathy in a murine model by the application of hyperbaric oxygen (HBO2). In this study we introduce a histologic morphometric technique for assessing fibrosis in the submucosa of these same animal specimens and relate this assay to the previous results. The histologic morphometry, like the previous gross morphometry and compliance assays, demonstrates a significant protective effect for HBO2. The present assay is related to the previous assays in a statistically significant fashion. The predictive value for the histologic morphometric assay demonstrates a sensitivity of 75% and a specificity of 62.5%. The applicability of this assay to other organ systems and its potential superiority to the compliance assay are discussed.

Hyperbaric oxygen an adjunctive treatment for delayed radiation injuries of the abdomen and pelvis.

Radiation therapy is often utilized as adjunctive or primary treatment for malignancies of the abdomen and pelvis. Radiation complications are infrequent, but can be life threatening or significantly diminish the quality of life. Radiation necrosis is an approved indication for hyperbaric oxygen (HBO2). Previous publications have reported results in treating delayed radiation injuries involving many sites. This paper reports the experience of a single physician group in treating delayed injuries of the abdomen and/or pelvis. Forty-four such patients have been treated since 1979. Of the 41 patients available for follow up, 26 have healed; 6 failed to heal; and 9 patients had an inadequate course of therapy (fewer than 20 treatments). Especially encouraging was the resolution of fistulae in six of eight patients with only three requiring surgery for closure. Overall, the success rate in patients receiving at least 20 HBO2 treatments was 81%. Hyperbaric oxygen is a useful adjunct in treatment of delayed radiation injuries of the pelvis and abdomen.

Hyperbaric oxygen as an adjunctive treatment for delayed radiation injury of the chest wall: a retrospective review of twenty-three cases.

Since 1979, 23 cases of radiation-induced chest wall necrosis have been treated in the Hyperbaric Medicine Departments of Southwest Texas Methodist Hospital and the Nix Hospital, San Antonio, Texas. Eight cases involved soft tissue only. Six of eight (75%) patients with soft tissue involvement healed without requiring surgical debridement, although four patients (50%) did have flaps or grafts. Fifteen patients had bony and soft tissue necrosis. Eight of these patients (53%) resolved with adjunctive hyperbaric oxygen (HBO), but all required aggressive surgical debridement including skeletal resection. Four (27%) had reconstructive flaps as well. Six patients (40%) with bony necrosis who had either no or incomplete debridement failed to heal. Three patients (13%)(two soft tissue and one bony) were found to have residual tumor during HBO and were discontinued from treatment. HBO is an effective adjunctive therapy for soft tissue chest-wall, radiation-induced necrosis, but must be coupled with appropriate debridement to include surgical removal of all necrotic bone to ensure a successful outcome of bony plus soft tissue necrosis.

Hyperbaric oxygen as a prophylaxis for radiation-induced delayed enteropathy.

This trial was accomplished in C3H mice to determine whether hyperbaric oxygen (HBO) could be administered to prevent delayed radiation enteropathy. Fifty mice randomized into two equal groups received 30 Gy abdominopelvic irradiation in 10 fractions. The study group received a course of 30 HBO treatments beginning 7 weeks after the radiation exposure. The control group received only housing and nutritional support after irradiation. A third group of three animals had no radiation or HBO. All animals were sacrificed 7 months after radiation. Animals were inspected grossly for signs of enteropathy. In addition, a special stretch apparatus was used to quantify narrowing and rigidity of ileum just proximal to the ileocecal junction. Those animals who received HBO had fewer gross signs of enteropathy and had less narrowing and less rigidity in their harvested bowel segments. These differences were highly statistically significant. Treatment with HBO drastically reduces signs of radiation enteropathy. Further study including clinical trials are recommended.

Does hyperbaric oxygen have a cancer-causing or -promoting effect? A review of the pertinent literature.

We reviewed all known published reports or studies related to a possible cancer-causing or growth-enhancing effect by hyperbaric oxygen. Published articles were retrieved using Medline searches for the period 1960-1993. Additional references were obtained from bibliographies included in those articles discovered in the computer search. Also, hyperbaric medicine text books and the published proceedings of international hyperbaric conferences were visually searched. Studies and reports discovered in this fashion and related to the topic were included in the review. Twenty-four references were found: 12 were clinical reports, 11 were animal studies, and 1 reported both an animal study and a clinical report. Three clinical reports suggested a positive cancer growth enhancement, whereas 10 clinical reports showed no cancer growth enhancement. Two animal studies suggested a positive cancer-enhancing effect, and 10 animal studies showed no such effect. (The report that included both animals and humans is counted in both groups). The vast majority of published reports show no cancer growth enhancement by HBO exposure. Those studies that do show growth enhancement are refuted by larger subsequent studies, are mixed studies, or are highly anecdotal. A review of published information fails to support a cancer-causing or growth-enhancing effect by HBO.

Hyperbaric oxygen as an adjunctive treatment for severe laryngeal necrosis: a report of nine consecutive cases.

Laryngeal necrosis is a rare complication of therapeutic radiation, but when it does occur there is no established, definitive treatment and laryngectomy is frequently required. This report is a retrospective review of all patients referred for hyperbaric oxygen (HBO) therapy to a single hyperbaric medicine unit for treatment of their laryngeal necrosis between 1980 and 1985. Nine patients were in this series. One patient had had a vertical hemilaryngectomy and another a supraglottic laryngectomy before referral. Eight of the nine patients had a Chandler grade IV necrosis and the ninth had a Chandler grade III necrosis. All nine patients were able to maintain their voice until death or last follow up. Seven of the nine patients maintained good voice quality while two exhibited some hoarseness. All patients with tracheostomies were able to be decannulated, and all patients with fistulae had these closed. No untoward reactions to HBO occurred. Based on this review, HBO is recommended as a therapeutic option whenever laryngeal necrosis occurs and there is a chance to save the larynx.

Hyperbaric oxygen and the cancer patient: a survey of practice patterns.

A questionnaire was sent to 179 clinical hyperbaric medicine facilities to survey treatment policies and referral patterns for patients with a history of malignancy. Eighty-five surveys were returned. Most respondents indicated that they would accept patients with a history of malignancy for either adjuvant or emergent hyperbaric oxygen (HBO). Depending on specific circumstances, from about one third to one half of respondents believed that such patients should be informed of a theoretical potential for tumor acceleration or reactivation. An overwhelming majority had not personally attended nor had they been told by colleagues of cases of patients whose malignancy had been activated or accelerated by HBO. A large majority felt that referring physicians did not believe that HBO was carcinogenic, and that referrals were not prevented by such concerns. Seven percent believed that HBO is potentially carcinogenic. Forty-two percent of respondents felt that they might be at risk for malpractice litigation if a patient had reactivation or acceleration of a malignancy. Among respondents to the questionnaire, there is a consensus that HBO does not have cancer-promoting or accelerating properties.

Hyperbaric oxygen as prophylaxis or treatment for radiation myelitis.

This animal study was designed to investigate HBO as a treatment or prophylaxis for radiation myelitis. All animals received identical spinal cord radiation doses of 69 Gy in 10 daily fractions. Group I received no HBO; group II began HBO at the onset of signs of myelitis; group III received HBO with prophylactic intent beginning 6 wk after irradiation; and group IV received both modalities on the same day, but radiation always preceded HBO by at least 4 h. HBO consisted of 90 min oxygen at 2.4 atm abs for 20 daily treatments. Animals were objectively assessed for the loss of certain neurologic reflexes indicative of four levels of myelitis. Although all animals progressed to severe myelitis, group III animals had group-averaged levels of myelitis consistently less than control. The differences were statistically significant for several weeks. Group IV animals progressed to severe myelitis much more rapidly than any other group. Additional study is justified by this trial. Key questions to be answered include the optimal timing of HBO to produce a beneficial rather than detrimental effect.