WSSA Glasgow.

Methods	Study design: 3‐arm RCT Country: Scotland Study period: 1972‐1977 Inclusion criteria: aged ≤ 76 years, operable breast cancer, no deep fixation or skin involvement, no fixation of axillary lymph nodes Exclusion criteria: none reported Length of follow‐up: 5 years in EBCTCG 1990
Participants	Simple mastectomy with radiotherapy to the chest wall but not to nodal areas (Arm A) vs simple mastectomy with radiotherapy to both chest wall and nodal areas (Arm B) vs simple mastectomy with axillary clearance and radiotherapy to the chest wall but not to nodal areas (Arm C) No. in trial arm: Arm A: N = 123; Arm B: N = 94; Arm C: N = 118 Age median and range: not reported Stage distribution: not reported Proportion node positive: Arm A: N = 16/123; Arm B: N = 9/94; Arm C: N = 17/118 Pathological type of breast cancer: not reported
Interventions	Simple mastectomy with radiotherapy to the chest wall but not to nodal areas (Arm A) vs simple mastectomy with radiotherapy to both chest wall and nodal areas (Arm B) vs simple mastectomy with axillary clearance and radiotherapy to the chest wall but not to nodal areas (Arm C)
Outcomes	Overall survival, local recurrence
Axillary node surgery	Minimum no. nodes to be removed according to protocol: see the next 3 lines Arm A: Protocol specifies no disturbance of nodes. Arm B: Protocol specifies no disturbance of nodes. Arm C: Axillary contents were removed. Method of node pathological analysis: not reported Further treatment for node‐positive cases: no
Radiotherapy	Arm A: Radiotherapy to chest wall (42 Gy in 2.1 Gy fractions) Arm B: Radiotherapy to chest wall (42 Gy in 2.1 Gy fractions) and nodal areas, including axilla and supraclavicular fossa (42 Gy in 2.1 Gy fractions) Arm C: Radiotherapy to chest wall (42 Gy in 2.1 Gy fractions) RT same in all trial arms? no
Hormone and chemotherapy	Not reported
Notes	Study included 3 arms: 1. Simple mastectomy with RT to chest wall but not to nodal areas; 2: Simple mastectomy with RT to both chest wall and nodal areas, including axilla and supraclavicular fossa; and 3: Simple mastectomy with axillary clearance plus RT to chest wall but not to nodal areas: results derived from arms 1 and 3 only. Data from meta‐analysis forest plot only Central randomisation Sealed cards Baseline differences? not reported Intention‐to‐treat analyses? not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Numbered envelopes: It is unclear how sequence was generated.
Allocation concealment (selection bias)	Unclear risk	Sealed envelopes: It is unclear whether envelopes were opaque.
Blinding of outcome assessment (detection bias) Disease control in the axilla	Unclear risk	This was not reported.
Blinding of outcome assessment (detection bias) Breast cancer recurrence	Unclear risk	This was not reported.
Blinding of outcome assessment (detection bias) Short term adverse events	Unclear risk	Outcome was not reported.
Blinding of outcome assessment (detection bias) Long term adverse events	Unclear risk	Outcome was not reported.
Incomplete outcome data (attrition bias) Survival	Low risk	Data appear to be available for all included participants.
Incomplete outcome data (attrition bias) Axillary recurrence	Low risk	Data appear to be available for all included participants.
Incomplete outcome data (attrition bias) Breast cancer recurrence	Low risk	Data appear to be available for all included participants.
Incomplete outcome data (attrition bias) Short term adverse events	Unclear risk	Outcome was not reported.
Incomplete outcome data (attrition bias) Long term adverse events	Unclear risk	Outcome was not reported.
Selective reporting (reporting bias)	Unclear risk	Short‐term and long‐term adverse events were not reported.