OVER.

Methods	Study design: Multicentre RCT Method of randomisation: permuted block design Exclusions post randomisation: EVAR = 17 (2 refused, 2 died, 1 repair aborted, 12 had OSR); OSR = 21 (4 refused, 1 died, 3 aborted, 13 had EVAR) Losses to follow up: 2 (both in EVAR group) Intention‐to‐treat analysis: Yes
Participants	Country: USA Setting: Hospital (42 centres) Recruitment: 15 October 2002 to 15 October 2008 Numbers: 881 (EVAR = 444; OSR = 437) Mean age (SD): EVAR = 69.6 years (7.8); OSR = 70.5 years (7.8) Inclusion criteria: AAA with a maximum external diameter in any plane greater than or equal to 5 cm An iliac aneurysm (associated with an AAA) with a maximum external diameter in any plane greater than or equal to 3 cm AAA greater than or equal to 4.5 cm and the AAA has increased by greater than or equal to 0.7 cm in diameter in 6 months An AAA greater than or equal to 4.5 cm and the AAA has increased by greater than or equal to 1 cm in diameter in 12 months An AAA greater than or equal to 4.5 cm and the AAA is saccular (i.e. a portion of the circumference of the aorta at the level of the aneurysm is considered normal based on CT scan or MRI) An AAA greater than or equal to 4.5 cm and the AAA is associated with distal embolism.as measured from two imaging studies (ultrasound CT scan or MRI) within the appropriate interval, the later one within 6 months of randomisation Exclusion criteria: Participant has had a previous AAA repair procedure Evidence of AAA rupture by imaging test AAA is not elective (i.e. urgent or emergent operation, usually due to suspected rupture) Likelihood of poor compliance to the protocol Participant refused randomisation Physician refused randomisation
Interventions	Treatment: EVAR Control: OSR
Outcomes	Primary: Long‐term all‐cause mortality Secondary: 1) Procedure failure 2) Short‐term major morbidity (i.e. myocardial infarction, stroke, amputation or renal failure requiring dialysis) 3) Inhospital and intensive care unit stay 4) Other complications such as incisional hernia or claudication 5) HRQoL 6) Erectile dysfunction
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation was performed by 'permuted block design'
Allocation concealment (selection bias)	Low risk	Allocation was made only after baseline information was obtained and eligibility verified
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Blinding of participants and operating surgeons not feasible in such a study
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcomes were adjudicated by a blinded outcomes assessment committee
Incomplete outcome data (attrition bias) All outcomes	Low risk	Analysis was intention‐to‐treat basis; all participants accounted for
Selective reporting (reporting bias)	Low risk	Reported on all predefined outcomes
Other bias	Low risk	None identified

AAA: abdominal aortic aneurysmCT: computed tomography
 EVAR: endovascular aneurysm repair
 HRQoL: health‐related quality of life
 MRI: magnetic resonance imaging
 OSR: open surgical repair
 RCT: randomised controlled trial
 SD: standard deviation
 SVS/AAVS: Society for Vascular surgery/American Association of Vascular Surgery