Manchester.

Methods	Study design: RCT Country: UK Study period: 1970‐1975 Inclusion criteria: new cases of clinical stage II (T1‐2, N1, M0) breast carcinoma Exclusion criteria: males, women aged > 70 years, history of cancer of the opposite breast, intercurrent disease, unavailable for follow‐up, pregnancy and lactation Length of follow up: 5‐10 years
Participants	No. in trial arms: simple mastectomy + postoperative radiotherapy (PORT): N = 159; ALND: N = 149 Age: simple mastectomy + PORT: mean (SD) = 55.2 (9.6) years; ALND: mean (SD) = 55.1 (9.9) years (latter value includes only N = 148) Stage distribution: T2 = 83% in both groups Proportion node positive: not reported Pathological type of breast cancer: not reported
Interventions	Simple mastectomy (removal of the whole breast including pectoral fascia but without intentional removal of any axillary node; thin skin flaps were to be avoided and transverse incisions preferred) + PORT vs radical mastectomy (removal of the whole breast with dissection of axillary nodes; removal of pectoral muscles up to the individual surgeon)
Outcomes	Local recurrence rate, breast cancer death, overall survival
Axillary node surgery	Minimum no. nodes to be removed according to protocol: not reported Nodes removed clearance arm: not reported Nodes removed sampling arm: NA Nodes removed SNLB: NA Method of node pathological analysis: not reported Further treatment for node‐positive cases: no
Radiotherapy	Simple mastectomy arm: Participants were treated with adjuvant radiotherapy according to 1 of the following 2 techniques.   1. Quadrate technique (3 fields (300 kV) at a tangent to the chest wall, irradiating the chest wall, the parasternal region and the axilla; also a field to the supraclavicular fossa and a posterior field to the apex of the of the axilla (est dose 3700 rads in 3 weeks); or 2. Peripheral and tangent pair technique as follows. a. Single megavoltage (4 MV) field consisting of irradiation of the parasternal, supraclavicular and axillary regions from the front (given dose 4000 rads in 3 weeks); or b. Parallel pair of fields to the chest wall, 300 kV (mid‐dose 3000 rads in 3 weeks; max dose to the skin 3800‐4500 rads). RT same in all trial arms? no. RT given only in simple mastectomy arm
Hormone and chemotherapy	Both arms: Participants who were premenopausal or < 3 years postmenopausal were offered artificial menopause by x‐ray or surgical castration.
Notes	Treatment of N = 20 and 16, respectively, deviated from protocol in the simple mastectomy + PORT and radical mastectomy arms. However, all participants were analysed according to randomised treatment allocation (i.e. intention to treat‐analyses were performed). Baseline differences? Paper states that the 2 groups of participants were similar with respect to age, menopausal status and tumour site within the breast. Intention‐to‐treat analyses? Paper states that intention‐to‐treat analysis was employed.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Patients were randomly allocated, with stratification by surgeon, to one or other of the treatment groups under comparison." (Lythgoe 1978, page 744). No additional details were provided.
Allocation concealment (selection bias)	Unclear risk	"Patients were randomly allocated, with stratification by surgeon, to one or other of the treatment groups under comparison." (Lythgoe 1978, page 744). No additional details were provided.
Blinding of outcome assessment (detection bias) Disease control in the axilla	Unclear risk	No details were provided.
Blinding of outcome assessment (detection bias) Breast cancer recurrence	Unclear risk	No details were provided.
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 participants.
Incomplete outcome data (attrition bias) Axillary recurrence	Low risk	Data appear to be available for all participants.
Incomplete outcome data (attrition bias) Breast cancer recurrence	Low risk	Data appear to be available for all 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.