Whitney 1999.

Methods	RCT 1986 to 1990
Participants	388 patients Stage IIB to IVA
Interventions	Radiotherapy plus hydroxyurea versus concomitant chemoradiotherapy (cisplatin, 5FU)
Outcomes	Survival, disease‐free survival, local and distant recurrence,acute toxicity
Notes	Only included in the sensitivity analysis due to use of additional hydroxyurea on the control arm only
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Data checks on IPD provided suggest adequate sequence generation
Blinding (performance bias and detection bias) All outcomes	High risk	Trial was not blinded due to nature of treatment interventions
Incomplete outcome data (attrition bias) All outcomes	Low risk	IPD provided for all outcomes except late toxicity
Selective reporting (reporting bias)	Low risk	N/A (IPD supplied for all outcomes except late toxicity)
Other bias	Low risk	Data checks on IPD provided suggest study is free of follow‐up bias