Although hyperbaric oxygen has been used as a treatment for patients with chronic intestinal syndromes following pelvic radiotherapies, a randomized, double-blind, placebo controlled phase 3 clinical trial found no evidence to justify its use.1

Investigators sought to provide concrete data regarding clinical benefits of the use of the treatment in this setting.

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The HOT2 trial included 84 adult patients with chronic gastrointestinal symptoms for 12 months or longer after radiotherapy and persisted despite at least 3 months of medical care and no cancer recurrence. Participants were randomly assigned 2:1 to receive either treatment in a hyperbaric chamber or placebo.

Those in the hyperbaric arm (n = 55) breathed 100% oxygen at 2.4 atmospheres of absolute pressure, while those in the placebo group (n = 29) breathed 21% oxygen at 1.3 atmospheres. Both groups received 90-minute exposures, once daily, 5 days a week for 8 weeks.

A total of 75 (89%) patients returned the IBDQ 2 weeks after treatment, and 79 (94%) returned it 12 months after treatment.

In an analysis of 46 participants in the active treatment group and 23 participants from the control group, results showed no significant differences in the change of IBDQ bowel component score between the groups (Mann-Whitney U score 0.67; P = .50).

No difference were found in another analysis of 29 participants from the active treatment group and 11 participants in the placebo group in terms of change of IBDQ rectal bleeding score (U score 1.69; P = .092).

Common adverse events in both groups included eye refractory changes (11% control group vs 30% in active treatment group), increased fatigue (11% vs 4%, respectively), and ear pain (21% vs 28%, respectively). Eight patients experienced severe adverse events: 2 grade 3 tonsillitis events requiring surgery occurred in 2 patients from the control group. In the treatment group, 1 patient was diagnosed with recurrent cancer of the vulva, and 6 serious adverse events occurred in 6 patients. None were treatment-related.

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Considering that no evidence was found to link the use of hyperbaric oxygen chamber with patient benefit, the authors concluded that “These findings contrast with evidence used to justify current practices, and more level 1 evidence is urgently needed.”  


  1. Glover M, Smerdon GR, Andreyev HJ, et al. Hyperbaric oxygen for patients with chronic bowel dysfunction after pelvic radiotherapy (HOT2): a randomised, double-blind, sham-controlled phase 3 trial [published online ahead of print December 15, 2015]. Lancet Oncol. doi: 10.1016/S1470-2045(15)00461-1.