Henk 1977a

Methods	RCT stratified by site of tumour (nasal and oral, laryngeal, laryngopharyngeal and other) with allocation concealment not clear, method of randomisation not stated. Patient, outcome assessors and treating team all aware of allocation. No indication of power calculation
Participants	295 adults with SCC of the head and neck where radiotherapy was the treatment of choice. 143 allocated to HBOT and 152 to control Dropouts identified (18 from HBOT group, 1 from control) but not included in analysis
Interventions	Control: between 3500 and 4500 rads in 10 fractions over 3 weeks HBOT: same regimen, pressure and time not specified but likely to have been 3 ATA for 30 to 40 minutes total exposure time
Outcomes	Death at 1 to 5 years, local control of tumour at 3 months, local recurrence rates at 1 to 5 years, significant radiation tissue effects at 6 months
Notes	Other reports of this trial in Henk 1974, Henk 1975, Kunkler 1968 Schulz rating: randomisation: C; allocation concealment: B; selection bias: B; blinding: C
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear