We report the results of a prospective controlled trial of the effect of hyperbaric oxygen as an adjuvant in radiotherapy of head and neck cancer. Patients were allocated randomly to treatment in oxygen or air. The radiotherapy in both groups was identical in planning, dose, and fractionation–i.e., 3500 rads in 10 fractions in 3 weeks. There was no difference in the survival rate between the two groups. However, significantly better local tumour control was seen in the hyperbaric-oxygen group, particularly in smaller lesions; there was significantly greater need for salvage surgery in the air group. Radiation effects on normal tissue appeared somewhat greater in the oxygen series, especially on laryngeal cartilage.

Henk, Kunkler, Smith, , , , , , (1977). Radiotherapy and hyperbaric oxygen in head and neck cancer. Final report of first controlled clinical trial. Lancet (London, England), 1977 Jul;2(8029):101-3. https://www.ncbi.nlm.nih.gov/pubmed/69191