Ehrenpreis 2005.

Methods	Double‐blind RCT. Duration of study: not reported Follow‐up: at 90 days
Participants	19 people with radiation proctopathy (at least 2 symptoms with a severity score of 3 on at least a weekly basis), however, one participant from each group did not take a single dose of study medication and were therefore excluded from analysis (n = 17). Sex (M/F): 15/2 Comparable groups with respect to baseline RPSAS Dropouts: 1 (reason not explained), but included in final analysis
Interventions	Intervention: Retinol palmitate 10,000 IU by mouth for 90 days Comparator: Identical placebo capsules
Outcomes	Reduction in the RPSAS scores after 30 days for 90 days
Notes	5 placebo non‐responders who were crossed over to Tx responded
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number system
Allocation concealment (selection bias)	Low risk	Neither the investigators nor participants were aware of who was receiving intervention treatment or placebo
Blinding (performance bias and detection bias)	Low risk	Double‐blinded study (participants and investigators were blinded)
Blinding of outcome assessment subjective	Low risk	Double‐blinded study (participants and investigators were blinded).
Blinding of outcome assessment objective	Low risk	Double‐blinded study
Incomplete outcome data: subjective outcomes	Low risk	ITT analyses was performed, number of drop‐outs reported, however reason for drop‐out not reported
Incomplete outcome data: objective outcomes	Low risk	ITT analyses was performed, number of drop‐outs reported, however reason for drop‐out not reported
Selective reporting (reporting bias)	Unclear risk	No study protocol available, however all outcomes mentioned in the methods section had been addressed in the results section
Other bias	Low risk	No indications of other bias