NCIC‐CTG MA21b.

Methods	See details in NCIC‐CTG MA21a
Participants	See details in NCIC‐CTG MA21a
Interventions	Three‐arm trial. For MA21b: ARM 1 (CEF): CEF × 6 28‐day cycles (cyclophosphamide 75 mg/m² orally days 1 to 14, epirubicin 60 mg/m² days 1 and 8, fluorouracil 500 mg/m² days 1 and 8) ARM 3 (AC‐T): AC × 4 21‐day cycles (doxorubicin 60 mg/m², cyclophosphamide 600 mg/m²) followed by T × 4 21‐day cycles (paclitaxel 175 mg/m²)
Outcomes	See details in NCIC‐CTG MA21a
Notes	See details in NCIC‐CTG MA21a
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	See NCIC‐CTG MA21a
Allocation concealment (selection bias)	Low risk	See NCIC‐CTG MA21a
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	See NCIC‐CTG MA21a
Blinding of outcome assessment ‐ OS (detection bias)	Low risk	See NCIC‐CTG MA21a
Blinding of outcome assessment ‐ DFS & Toxicity (detection bias)	Unclear risk	See NCIC‐CTG MA21a
Incomplete outcome data (attrition bias) All outcomes	Low risk	See NCIC‐CTG MA21a
Selective reporting (reporting bias)	Low risk	See NCIC‐CTG MA21a
Other bias	Low risk	See NCIC‐CTG MA21a