Institut Curie.

Methods	Study design: RCT Country: France Study period: 1982‐1987 Inclusion criteria: female patients aged < 70 years with no history of previous cancer, no previous treatment, presenting with a unilateral invasive carcinoma < (Louis‐Sylvestre 2004) or ≤ (Cabanes 1992) 3 cm, no clinically involved axillary lymph node (N0, Louis‐Sylvestre 2004; or N0‐N1a, Cabanes 1992) and non‐metastatic (M0) disease Exclusion criteria: patients age > 70 years with cancer at another site (apart from basal cell carcinoma and intraepithelial carcinoma of the cervix), patients who could not be regularly followed up at the Institut Curie Length of follow up: median (range) = 180 (12‐221) months
Participants	No. in trial arms: RT: N = 332; ALND: N = 326 Age: RT: mean = 50.6 years; ALND: mean = 52 years Stage distribution: RT: T1, N = 233; T2, N = 99; clinical N0, N = 256; clinical N1a, N = 76. ALND: T1, N = 207; T2, N = 119; clinical N0, N = 270; clinical N1a, N = 56 Proportion node positive: 68/322 who received ALND (i.e. 2 RT participants and 320 ALND participants (see also notes)) Pathological type of breast cancer: RT: invasive intraductal, N = 286; other, N = 46. ALND: invasive intraductal, N = 268; other, N = 58
Interventions	Lumpectomy (wide local excision of the tumour with macroscopically healthy margins) + RT to the breast and axillary and internal mammary lymph nodes vs lumpectomy (wide local excision (with macroscopically healthy margins) + axillary dissection (limited to nodes inferior to the axillary vein; level I and lower level II nodes) + RT to supraclavicular and internal mammary lymph nodes in participants with histologically confirmed metastatic lymph nodes. If medial or central tumour was diagnosed in this group, internal mammary lymph nodes were also irradiated.
Outcomes	Overall survival, local and lymph node recurrence, metastases, disease‐free survival
Axillary node surgery	Minimum no. nodes to be removed according to protocol: not reported Nodes removed clearance arm: see "Interventions" Nodes removed RT arm: none Method of node pathological analysis: not reported Further treatment for node‐positive cases: yes (hormone or chemotherapy)
Radiotherapy	Both arms: 55 Gy fractionated over 6 weeks to the breast. 10‐15 Gy boost to the tumour bed Axillary nodes: 50 Gy Internal mammary nodes and supraclavicular nodes: 45 Gy RT same in all trial arms? no
Hormone and chemotherapy	Both arms: Adjuvant medical treatment was available depending on the number of lymph nodes invaded and menopausal status. Chemotherapy: RT: N = 9; ALND: N = 19 Hormone therapy: RT: N = 8; ALND: N = 14
Notes	The treatment protocol was not followed in 15 participants (RT: N = 2, N1 patients underwent dissection; N = 4, underwent mastectomy; ALND: N = 6, did not have dissection (and consequently received no treatment of the axilla); N = 3, underwent mastectomy). In addition, 7 N1 participants (RT: N = 6; ALND: N = 1) were enrolled, although they should not have been included in the protocol. N = 11 were lost to follow‐up at 5 years, and N = 58 were lost to follow‐up at 10 years, but unclear to which group they belonged Baseline differences? Groups appear to be comparable at baseline. Intention‐to‐treat analyses? Cabanes (1992) and Louis‐Sylvestre (2004; from which data were extracted): Both state that participants with protocol violations were maintained in the group to which they had initially been assigned for purposes of statistical analysis, which was conducted in an intention‐to‐treat fashion.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Paper states that randomisation was done by sealed envelopes (equilibrated every 6 participants) in the operating theatre after verification that participants satisfied the inclusion criteria. No further details were provided.
Allocation concealment (selection bias)	Unclear risk	See cell above.
Blinding of outcome assessment (detection bias) Disease control in the axilla	Unclear risk	No details were reported.
Blinding of outcome assessment (detection bias) Breast cancer recurrence	Unclear risk	No details were 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	Unclear risk	N = 11 were lost to follow‐up at 5 years; N = 58 were lost to follow‐up at 10 years, but it is unclear to which group they belonged.
Incomplete outcome data (attrition bias) Axillary recurrence	Unclear risk	See cell above.
Incomplete outcome data (attrition bias) Breast cancer recurrence	Unclear risk	See cell above.
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	Long‐term and short‐term adverse events were not reported.